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Online Solar Manual for Homeowners

Light On The Earth: The Solar Option

By Jonathan R. Cole
© 2008
With Andrew Walsh

Copyright © 2008 Jonathan R. Cole. All rights reserved.
ISBN: 1-4392-5855-4 ISBN-13: 978-1-4392-5855-2
Library of Congress Control Number: 2009909621
Latest revision -  August 2013

“You must be the change you wish to see in the world.”
                                                        Mahatma Gandhi

This Online Book Is Copyrighted
It is meant for people who wish to read it on their computer.
The Appendix of Technical Information is not included in this online version.
The printed book is available at
Click on Amazon to get the book

If you are a do-it-yourself person, plans, schematics and equipment lists.are available from Light on the Earth Systems for reasonable fees. Inquire at 2earthlight at

Table of Contents (not Active)
Introduction to Solar Energy
What is a Solar Energy System?
Calculating Energy Efficiency
Where to Start? How to Reduce Energy Use
The Photovoltaic or PV electrical system
Wiring the PV Panels
The Inverter
How to Choose the Right Backup Power Source
Financing Solar
Photo Credits
About the Author:
Author: Jonathan Cole
With: Andrew Walsh

Introduction to Solar Energy
This information is formulated for those interested in making a change in the way they think about and utilize energy, with the goal of allowing the installation of a solar powered energy system for a household or small business that is easy to use, reliable, and cost-effective.
   Whether you are a do-it-yourselfer or need to oversee the work of a professional electrician or other solar installer, this is the information that you and your electrician need, to make sure that a durable, safe, and cost-effective system is installed. In many cases, a professional electrician is required, particularly if you have no experience working with electricity. In cases where the equipment is UL approved and is not hard-wired but can be connected and disconnected by means of a standard electrical plug, you may not need a permit depending on your local regulations.
   In order to utilize this technology, you need 5 to 20 square yards (depending on energy requirements) of space on a roof or in a yard, facing south, that remains free of shadow from 9:00 AM to 4:00 PM. This is for the solar energy collectors. You also need to have additional space for storage of the supporting equipment which can be a closet that is conveniently located for connecting all the components together. Of course, these installations are semi-permanent, so it is most practical if you own the property or have a long-term lease.
   Some of you may be familiar with some of the issues discussed here. If so, bear with us as we develop a logical process to the attainment of our goal.
   Why is this information of value? Why can’t you simply hire a professional to make all the decisions for you? The answers to these questions are straightforward. Each individual, family, or business must weigh costs and advantages of each element of an energy system that matches cost and performance to the individual requirements of equipment budget, convenience, maintenance, and ongoing costs.
   It is difficult for a professional to accomplish this without making an in-depth study of your financial situation, your lifestyle, and other intangibles such as a commitment to living lightly on the earth. This can be an intrusion on your privacy and can well result in an unsatisfactory energy system, since so much subjective interpretation would be required by the professional.
   It is not that much different than buying an appliance such as a refrigerator or washer-dryer. In this instance you are buying an energy appliance. Since most people have left that to the central power company, you don’t yet have the experience to purchase the right energy appliance to meet your needs. This means that you must be willing to learn, to think and evaluate, and to make decisions about the best way to accomplish your personal energy use requirements.
   If your commitment to changing your energy use habits is decided upon and you are willing to do a little focusing and concentrating on the basic issues involved, I believe that the level of learning that is required can be readily achieved by a 16-year-old and, therefore, should be very straight-forward for the majority of people. I hope you are one of the committed. If so, this book is definitely for you.  
   To start on the path to a clean, green energy conscience, it is helpful to consider the historic path that has led our society to the present multifaceted energy problem.
   In earlier times, people discovered fire, which is the most basic transformative use of energy. Fire releases the energy contained in combustible substances allowing it to be used for cooking, heating, and powering various types of engines for transportation, electrical generation, and many industrial processes. The advantage of fire is that it is easily initiated and makes use of the relatively high density of energy stored in fuels. Whether the fuel is wood, alcohol, coal, oil, or natural gas, the principle is the same.
   The comforts and conveniences derived from this original energy technology have now become familiar to people in the most isolated areas of the world. The desire to achieve the modern standard of living attained in developed nations is now the worldwide ambition of many billions of people.
   However, the difficulty is that these fuel sources are limited and being rapidly depleted while simultaneously placing an increasingly destructive burden on the natural systems that are the foundation of our standard of living. In addition, we will still need these combustible fuels as feed-stocks for non-combustion benefits such as fertilizer, lubrication, and the manufacture of materials used in transportation, housing, and appliances. If we burn these basic resources, we will be left with an impoverished world where only a small minority can attain a comfortable life.
In the past, when the population was much smaller, the negative side-effects of combustion were considered to be bearable considering the benefits that were derived from combustion systems. These negative side effects include the health hazards of air, water and land pollution, and more recently the contribution to global climate change and the acidification of the oceans which threatens the habitability of the entire planet for all life forms including humans.
   We do not need to rehash the technical details of this problem. It is enough to note that the era of cheap combustion energy is rapidly coming to a close and it is in our personal interests to take the steps necessary to achieve our desired standard of living through different technical means. Fortunately, we have those means at our disposal. Now, we must learn how to effectively utilize the available technologies to harness the ultimate source of clean energy available to us—the sun.  
   So, what is the formula for this transformation?
Efficient equipment + low-waste strategies + solar energy = An affordable, high standard of living minus destructive global consequences.
   This has already been demonstrated and achieved by some, including myself. Now, we must as rapidly as possible disseminate the knowledge that will allow others to join in this energy evolution. This book intends to provide comprehensive real-world information that allows energy consumers to understand how to live in a solar-powered world. I personally hope that it will also dispel much of the mythology surrounding solar energy including the false ideas that it is unreasonably expensive or unreliable. In fact, solar technology is one of the most cost-effective and durable technologies ever devised by humans. With the current government incentives it is remarkably inexpensive to utilize solar. I did not use any of these incentives and still, the cost of my 40 year solar energy system with all the modern amenities was about the same as a late model used car that will last no more that 5-7 years. The myth of unaffordable solar energy is over!!
Please Note:
Updates and corrections to all information in this book will be posted at our companion web site. From there you can also contact the author, make suggestions, and purchase printed copies.

What is a Solar Energy System?
There are two fundamental types of solar energy systems. One type creates electricity and is generally called a photovoltaic or PV system. A photovoltaic system is an electronic, solid-state integration of roughly a half-dozen components that produces household electrical energy from the light of the sun. The other type is a system of heating; either for water, space heating, or drying. These systems convert the light of the sun into thermal energy. The more ways that you can utilize the sun to meet your energy needs, the less polluting forms of energy will be required to support your standard of living.
   It would be theoretically possible to eliminate all use of such polluting energy, but in many cases it is impractical because of expense or reliability. However, it is not difficult to attain an enormous reduction of such undesirable energy forms in an affordable way that will rapidly pay for itself in reduced costs. That is the goal of this book—to help you to understand the design and utilization of practical, cost-effective solar energy systems.

How to make a cost-effective, home-based energy system
First Step – Efficient Equipment
When you become your own energy provider, the economic consequences of waste become much more obvious. That is why the first step in designing a practical cost-effective system is to reduce inefficiency so that you require the smallest possible energy generating and storage system. The smaller the system, the less money is required for purchase and installation. Efficiency is the low hanging fruit that is most easily harvested. Even those who choose to stay connected to the electrical grid can benefit from this knowledge.
   This step involves looking at every energy consuming appliance that you require and determining if there is a more energy efficient product at a reasonable price. Investments in efficient equipment pay off quite rapidly in terms of saved energy costs regardless of where the energy comes from. This is quite simple to do because all products are labeled with their energy use.
   In the case of electrical products, that energy use is labeled as kWh (Kilowatt/Hour) or annual kWh (occasionally appliances are only labeled with volts and amps which can be multiplied to approximate watts per hour or Wh). One kWh is 1000 watts used per hour or 1000 wh. By comparing the numbers of kWh on the labels of appliances you can determine which products are the most efficient.       
   To get the amount of total energy required by an appliance, you can multiply the rated kWh times the number of hours per day (on average) that the appliance is in use. In the case of something like refrigeration, in order to compare models you can also calculate the energy use that is required per cubic foot of refrigerator space. 

   There are also very inexpensive meters available called “Kill-a-watt” meters that can be used to get an exact readout of the electrical energy use of any appliance. I purchased mine on Ebay for less than $20. I frequently use this meter to check on the efficiency of my equipment and to check for malfunctioning appliances. It has definitely saved me hundreds of times its cost.
   Very few devices require energy 24 hours a day. Most appliances cycle on and off either by your decision or by automated systems that use thermostats or timers. So the amount of total energy used is a function of how much time the equipment is actually on. If waste is minimized by making sure that equipment and appliances are not left running unnecessarily this can significantly reduce your energy needs and the costs of supplying them. 
   Many appliances have a standby function that allows the appliance to come on a little faster or keep a clock display going and other such minimal advantages. TVs, stereos, video players, microwave ovens, computers, printers and scanners, and many other devices have this standby function that uses a small amount of energy 24 hours a day. This invisible power draw can build up and become a significant energy cost. 
   A simple and cost-effective work-around for this problem is to run such equipment through a switched power strip or even more conveniently through a switched electrical outlet.
   Reducing energy-use that yields no advantage is a very cost-effective means of having a smaller, less costly solar energy system with little penalty.

Calculating Energy Efficiency
Energy efficiency is the calculation of how much energy is required to produce a given result. For example, the amount of energy that is required to cool one cubic foot of refrigerator space over a period of one year. If the refrigerator uses 380 kilowatt hours (kWh) per year, to cool 10 cubic feet (cf), then 380 kwh/10 cf = 38 kwh per cubic foot per year. Another refrigerator may use more or less energy to achieve the same result. If a refrigerator uses less energy, it is more efficient and vice versa.
   Energy efficiency is a complex topic that by itself could fill volumes. I will try here to give some simple examples of how it is calculated in order to demonstrate the fundamental principles. I will not use real quantities, but instead, will make approximations that can yield useful results.
   Let us say that at a certain place in the world the amount of solar energy reaching a surface on the earth that is perpendicular to the sun’s rays, on a clear day at noon time is equivalent to 750 watt hours (Wh) of electricity per square meter (Wh = watts generated in 1 hour). On this square meter, we place a photovoltaic (solar-electric) panel that is 20% efficient. However, since the sun’s energy varies over the daylight hours we have made measurements (provided conveniently in available charts in the Appendix of this book) that give us an average of 4 peak hours of sunlight per day in our location. We calculate the energy actually generated in this way:
     750 Wh x 4 (peak hours) = 3000 Wh/day = the total energy falling on the 1 square meter panel.
   At 20% efficiency of the solar panel, 3000 Wh/day x .20 = 600 Wh/day of electricity generated daily per square meter of panel. This is not much energy, so let us use 10 square meters of panels to provide us with a useful amount. Then we have:
     600 Wh/day x 10 = 6000Wh/day
If we use this energy directly we have perhaps 1% losses in the wiring, so:
     6000 Wh/day x .99 = 5940 Wh per day of electricity generated and delivered.
If we convert this electricity from direct current (DC) to alternating current (AC) in a device called an inverter that is 90% efficient, then:
5940 Wh/day x .90 = 5350 Wh/day of electricity generated and delivered as household AC power.
   If we use this energy to power an AC electric refrigerator whose motor uses 150 watts per hour (if it is running continuously) and is on 50% of the time over a 24 hour period, then it requires:
     150 Wh x .50 x 24 hours/day = 1800 Wh/day
   Normally a refrigerator is operational for 24 hours per day but it can be set to a slightly colder temperature that results in an average energy use of 160 Wh instead of 150Wh. It can then be turned off for 12 hours during the night with a timer. In this case the refrigerator uses:
     160 Wh x .50 x 12 hours/day = 960 Wh/day
We can see that by running the refrigerator at a slightly colder temperature, we have stored the electricity as cold and have saved:
     1800 wHr/day – 960 wHr/day = 840 wHr/day
   Now let’s say that our refrigerator is 85% efficient and we replace it with one that is 90% efficient (it remains on a timer to run only 12 hours/day). This yields a savings of 5% of the energy used by the less efficient model:
     960 Wh/day x .05 = 48Wh/day savings.
On an annual basis this would be:
     48 Wh/day x 365 days = 17,520Wh/year energy saved.
This is enough savings to run the refrigerator an extra:
     17,520 Wh/year / 912 Wh/day = 19.2 days/year. That’s nearly three weeks!
   Now, if we were to run our original refrigerator for 24 hours, then we must store that solar energy in a battery for use at night when there is no sun. This means that at least 50% of the energy used would have to go through the battery system which has an in/out efficiency of 90% at best. This means that:
     1800 Wh/day x .50 = 900 Wh/day from the battery.
   This half of the energy use that comes from storage in a battery requires an extra 10% of generated energy to make up for the losses in the battery system so it requires:
     900 Wh/day x .10 = 90 Wh/day extra, or 1890 Wh/day when run for 24 hours.
However, by choosing to run our refrigerator for 12 hours a day at a colder temperature, we are using:
     960 Wh/day instead of 1890 Wh/day—a savings of nearly half.
   By storing the solar energy as cold instead of in a battery we save energy because of the battery’s in/out losses. In addition, there are substantial costs to save energy in a battery. Commonly used batteries in such systems have a cost of about $0.15 per 1000 Wh stored, so we are saving this cost by not storing energy as electricity but instead storing it as its end-use function: cold. This means that we need a smaller battery system which also saves money. It also means we need fewer solar panels to power our house, a considerable savings.
   I have chosen a refrigerator as an example because refrigeration is one of the largest energy users in a household. (Of course, this is only an approximation, since the energy used also depends on the temperature in the kitchen and how often the refrigerator is opened). Our 10 square meters of solar panels are generating 6000 Wh per day of electrical energy with an actual delivered amount of 5,350 Wh after wiring and AC inverter losses. Our refrigerator is only using 960 Wh/day.
That leaves: 5350 Wh/day – 960 Wh/day = 4390 Wh/day
   What are we going to do with all of this extra energy? Maybe we need a smaller solar energy system! By utilizing efficient equipment and strategies for reducing waste we have made it possible to have a smaller, more affordable system.
Of course, efficiency is not the only consideration. Sometimes design aspects of appliances that add to the practical use, appearance, or longevity must be considered as well.
An example of efficient design is a hyper-efficient refrigerator available from Sun Frost that is only manufactured in limited production runs. It uses a fraction of the energy that the most efficient mass-produced models use. On the other hand, it costs up to five times more ($2,000+) than the garden variety refrigerator that can be had for about $400 and the Sun Frost is built from particle board which can quickly degrade in the presence of moisture. The storage compartments (door shelves, drawers, etc.) are poorly designed or non-existent, and the appliance is oversized, very bulky, and heavy. 
   So efficiency, just like everything else in life, is a balance of forces. Careful consideration of practicality, durability, and actual energy use must be undertaken. I was able to find an Energy Star refrigerator on sale at Home Depot that cost around $650 and uses an estimated average of 360 kwHr per year or a little less than 1 kWh per day. By putting a timer on the refrigerator I was able to reduce its energy use by nearly 50% with no noticeable loss of performance. Look for Energy Star appliances here: I am planning to enclose the fridge in a box with cool air circulating by means of a vent from under the house from which cooler air is drawn in by the rising and venting of heated air given off by the refrigerator. Because heated air naturally rises, the waste product of the refrigerator—heat—acts as the driver of a natural heat pump to keep the exterior of the appliance cooler than it would otherwise be. Of course, since heat flows into the refrigerator from the outside air temperature, keeping the exterior cooler means less energy is needed to keep the inside cool.

Where to Start? How to Reduce Energy Use
Different appliances that we use have a hierarchy of annual (long-term) energy requirements. This is useful to know because it shows where the most energy can be saved by upgrading to the most practical and efficient appliances. The best way to get the most efficiency gains per dollar is to start with those functions that use the highest average daily energy and then gradually work your way to the lower energy uses.
   This is a typical list from highest daily energy-use to lowest in the functions we generally require.
1.      Space heating and cooling (furnace/air conditioning)
2.      Water heating
3.      Refrigeration
4.      Water pumping (where applicable)
5.      Washer and dryer
6.      Lighting
7.      TV
8.      Power Tools (occasional use)
9.      Desktop computers, Laptop computers, Printers/scanners, Stereo equipment
10. Microwave (occasional use), Cooking appliances
11. Small electronic devices (cordless phones, rechargeable digital cameras, cell phones, etc.)

1.  Space Heating and Cooling
This function requires the most energy because much of the energy we use to achieve it ends up being lost through poor insulation, poor ventilation, or both. In some modern houses, particularly in Europe (very cold in the winter, very hot in the summer), architectural designs created for energy efficiency have brought this largest energy consumer to almost zero energy-use other than ambient heating from solar energy.
   This is accomplished by investments in insulation, double and triple glazed windows, generous caulking of every possible entry and exit for air, and by use of passive and active solar heating systems. These tightly sealed houses use heat-exchangers (like the radiator on a car) to heat up a controlled amount of fresh air brought into the house.
   Insulation, ventilation, and caulking are very cost-effective replacements for excessive energy use whether for heating or cooling. For example, my house requires more attention to cooling than heating because I live in a place that is generally warm. By the use of open ceilings, with insulation in the ceiling and simple vents in the floor and at the peak of the highest wall, as well as windows that provide cross ventilation, I am able to easily maintain a comfortable temperature at very little material cost and no energy cost.
   A couple of basic principles explain how this works. Under the parts of the house that never see any sun the earth remains cool, storing this coolness from the night when temperatures are much lower. In the day the air inside the house warms up and hot air rises. The rising air goes out through a screened vent at the peak of the highest wall. Cool air is drawn through a screened vent from under the house, replacing the hot air with cooled air. When this is insufficient, shaded windows on the north side of the house can be opened for additional sources of cooler air. This is the most basic type of passive climate control. The only moving parts are the vent doors that can be opened or closed by the occupant(s).
At night when the temperature cools down, the heat from the day can be trapped by closing the vents. Only on the coldest nights of the winter do I sometimes require the use of additional space heating from a small propane unit. The annual costs of my heating/cooling system are less than $50 per year.
   Active elements such as fans and blowers or automated temperature controlled vent doors can be added but in many cases are not required.
   For those who require heating—insulation, ventilation, and caulking are also very important as this reduces the amount of energy required to keep the building comfortable. Caulking can also be used to seal all possible cracks and small openings that allow insects to infiltrate. This is also an energy saving strategy, because damage and contamination from insects reduces the useful life of the building which is a significant investment in energy and materials (also a store of energy).
2. Water Heating
This is where you can get a big bang for your buck. Electric or gas water heating tanks are often the most costly energy appliance. A lot of savings can be had simply by installing a timer on your electric water tank (available for less than $50 at the hardware store). You do not need to be heating water at night when no-one is up to use it. Modern water tanks recover very quickly (less than an hour) from depletion of the hot water. If you set the timer to turn off at bedtime and turn back on an hour before you get up, you will save a lot of energy. This is also true, even if you have a solar water heater and use the electric or gas energy as backup. Water heating systems that use a tank for storage, can also benefit from enclosing the tank in a small insulated closet. Of course, nothing beats a solar hot water heater for low energy costs.
Solar water heating systems are very efficient with up to 80% energy efficiency. This is because a very high percentage of the light hitting the dark surface of a solar hot water heater is converted into thermal energy. All solar water heating systems employ black colored tubes filled with liquid (water or a working fluid-like anti-freeze for colder climates) connected at the top and bottom to a tank storage system. Generally, these tubes are in an insulated enclosure with a glass cover that prevents the heat from radiating back into the atmosphere.
   There are many types of systems with a wide range of costs. There are many examples of overly expensive and impractically designed equipment and systems.   
   So how do you choose the best system for your needs?
The most common, durable, and inexpensive type is called a flat plate collector. In this type of system a series of parallel tubes is connected at right angles, top and bottom, to header or collector tubes and the tube assembly is attached to black metal absorber plates. The entire system is mounted in an insulated box. This assembly has a special kind of glass on the front. This glass is shatter resistant and reduces heat loss. The outside of the glass has an anti-reflective coating so that sun will pass through with little loss.
   But in order to understand how to get the best system for your needs, there is much to consider.
   The sun does not always shine and over the year the hours of daylight can vary considerably. There are always more daylight hours during the summer than in the winter, fall, or spring. The shortest day is December 21, and the longest is June 21, with the day’s length gradually changing in between these times. There are cloudy days; sometimes dark gray clouds, sometimes light cloud-cover, and sometimes scattered clouds. In every case, solar energy can be collected but obviously the greatest yield is with a clear sky. (Although there is a surprising exception to this: when sunlight is reflecting off the edge of scattered clouds panels can generate up to 30% more than their rated capacity.) As a result of this variability, the sizing of a system is very important.
   From my experience, the best approach to sizing is to recognize that it is a balance of costs and total energy independence or autonomy. The way to minimize costs and maximize quality of life is to size the system a bit smaller than your actual use and then make up the difference with a highly efficient backup.
   There will always be a few times when the solar does not provide sufficient energy for your immediate needs. You could size your system to be so large that it would always have enough, but this would be very expensive and then most of the time you would have more hot water than you could possibly use. This would result in a constant draining of hot water from the system as the pressure relief valve is activated to reduce the pressure from too much heat in the system.
   Absolutely reliable energy supplies are most cost-effectively achieved with small backup systems that are not called upon very often, but are there when you need them. For a hot water backup system, I have chosen to incorporate a Takagi Jr. tank-less, instantaneous propane water heater that is computer controlled and highly efficient. This is by far the most efficient way to use fuel to create hot water. It allows you to have hot water in the rare instances that your reasonably sized solar hot water system does not provide enough. You end up using very little gas energy, while at the same time having the luxury of hot water at all times. Remember, we are working to create a system that is light on the earth and yet maintains our standard of living.
   My computer controlled, tank-less water heater measures the temperature of the incoming water and then only provides enough heat to warm it up to your preset temperature requirement. Thus, whenever the solar water heater provides water at the correct temperature, the tank-less backup heater does not turn on. If the solar heated water is insufficient, it provides just enough energy to heat it to your requirements and no more.
   A solar hot water heater does require a tank to store the heated water. The tank should be well insulated. As mentioned earlier, it can also be enclosed in a small closet that further reduces heat loss and protects the tank from the elements. Such a closet should have a door with good access to the tank, for maintenance.
   I recommend using a remote electronic thermometer, wall-mounted in a convenient location so that you can check the performance of your solar hot water system and learn about the daily cycles of energy so that you can time your energy use to availability when possible. For example, if you wash your clothes half way through the day, your solar hot water can be replenished before sunset.
   There are two types of solar hot water heaters: passive and active. The active system uses an electric pump to bring the hot water from the collector to the tank. The only advantage to this is that it lets you place your hot water collecting panels above the storage tank, for instance, on the roof. But there are many downsides to this type of system. The pump is the weak link. It will not last as long as the rest of the system in many cases. When it fails you have no hot water. Replacement is costly and inconvenient.Plus, the pump requires electricity. Power outages mean no solar hot water.
   I have, therefore, always chosen a passive system that requires no pump. This type of thermo-siphon system places the collector panel below the storage tank. The natural rising of heat causes the hot water to be circulated into the storage tank.
   These types of systems are less expensive and are nearly indestructible. In those that I have built, the collector panel is mounted on the ground at an appropriate angle and the tank is not more than 20 feet away and at least several feet higher than the output of the collector panel. The upper pipe of the panel connecting the panel output to the tank must continuously rise to the upper inlet on the tank. The cold water return pipe comes from the bottom of the tank and continuously drops to the inlet at the bottom of the collector panel. The continuous rise and drop of the pipes is necessary to allow the efficient thermosiphon pumping to occur without creating a trap where the heat cannot pass.
   There are also passive, integrated collector-tank models that can be roof mounted so you get the system off the ground. The down side of these roof mounted passive systems is that the tank is not necessarily close to the place where you need the hot water. As a result, you may have to run the water for a long time before it gets hot or else install a costly recirculation system that pumps hot water through your pipes. Such recirculation systems also tend to lose a lot of the heat stored in the water, so you require a larger more expensive system. 
Ground-mounted Thermo-siphon Solar Water heater

  If there is a ground mount location that is not shaded on the south side of the house, this is preferable because it takes the weight of the stored water off the roof and puts the system in a place that is easy to maintain. Ground mounted systems can be integrated into the landscaping with slow-growing plants that do not grow high. This also allows you easy access to periodically clean the glass, allowing the panel to operate at peak efficiency. Dust, mixed with rain, bird-droppings, leaves, etc., must be periodically cleaned from the glass—not that easy to accomplish in a roof-mounted system. I used a ground mounted passive system for over 20 years and despite lots of children and pets, the glass was never broken and the system never stopped producing hot water. No repairs, lower cost, easy maintenance—this is the direction to take for a high standard of living.
   Wherever the system is mounted, the pipes have to be well-insulated. Expanded foam tubing is available for this purpose, but should be impervious to UV light from the sun. All slits and bends in the insulation tubing should be taped to reduce heat-loss. The longer your pipe runs, the more they cost in piping and insulation.
I always try to reduce these unnecessary costs as much as possible by placing the solar collector in close proximity to the tank. Reducing unnecessary expenses gives you more to invest in the essential solar energy systems that yield the highest standard of living.
3. Refrigeration
Refrigeration, as mentioned earlier, is a technology that generates and stores energy as cold. Cold is actually just the absence of heat, but the food and liquids in your refrigerator retain this cold over long periods (12-24 hours) if the refrigerator is not opened. To reduce energy waste, it makes sense to keep your fridge stocked or if necessary to put containers of water or ice packs that will store the cold during the day, so it can be turned off at night.
   One of the most significant losses of this stored cold come from opening the door. This is particularly true of refrigerators with vertical doors. This occurs because the cold air inside the box is more dense and thus heavier than room temperature air and very rapidly falls out onto the floor drawing in the warm air. Fortunately, the air that falls out does not contain too much cold because it is a diffuse gas. Most of the cold is stored in the solids and liquids in the fridge. Still, the constant opening and closing of a refrigerator has a noticeable energy penalty. This is why many refrigerators have drawers at the bottom, where the coldest air settles and won’t empty when the door opens.
   Horizontal freezers prevent the cold from falling out and use much less energy per cubic foot of storage. These can actually be set up as highly efficient refrigerators, but because of the large footprint they may not readily fit in a kitchen and given the difficulty accessing items, most people choose a vertical refrigerator-freezer.
   Placement of the refrigerator is an important consideration. You never want sunlight shining on any part of it. Warming of the box causes the refrigerator to use more energy to maintain the cold temperature inside. Where possible, it makes sense to recess the refrigerator into the wall, either in a closet ventilated with outside air or even directly through a north-facing wall. This allows the cooler evening air to assist your refrigerator at night. Plus, kitchens that have a lot of heating and cooking appliances are less able to effect the refrigerator’s temperature.
   In a solar powered household it makes sense to run the refrigerator slightly colder than normal and using a heavy-duty 20 amp timer, turn it off during the night hours when the doors generally remain shut. This cold storage is very cost-effective and from my experience, as long as the fridge has adequate stocks of cold-storing materials, it makes no noticeable difference in performance. Another advantage of this regime is a reduction in the necessity for defrosting.
4. Water Pumping
Using an electric motor to power a water pump is quite energy-intensive. The larger the motor and the longer the duration of pumping, the more energy is required. A ½ horsepower motor driving a pump can use 500 watt/hr. That is 500 watts for one hour. That pump would use more electricity in 2 hours of running than my refrigerator uses in 24 hours. Pumps of this type are normally not required by households except in the case of a catchment water system that needs a pump to create water pressure or for pumping water from a well or cistern storage tank.
These systems have a pressurized tank that provides water flow for a short time. Then as the water is used, the pump must run to restore the pressure. The volume of pressurized water-use is directly proportional to the energy consumption. In systems such as this, it makes sense to create a gravity flow sub-system. This means elevating the collection tank on a hill or even a frame of some sort. Since water is very heavy, a solid foundation is required. For some uses, such as toilets, garden watering, and car washing, a gravity fed system may be adequate. Since these uses require minimal filtering, the pressure and volume may be adequate.     Taking this approach can save significant amounts of energy over time.
   A washing machine also has a water pump as part of its function. That is why washing machines use quite a lot of energy when the water is being pumped out. However, since it is used less frequently than a pressurizing water pump, its overall energy use is much lower.
   Small pumps, such as for aquariums or fountains, use a fairly small amount of energy but if they are always running it can add up. It pays to use the most efficient models you can find.
5. Washer and Dryer
The washing machine, as mentioned, uses a lot of energy due to the water pumping portion of its cycle. There are ways to reduce the consumption of energy by a washing machine. I have discovered that with currently available liquid detergents, the “normal” wash cycle for most cleaning jobs is excessive. Earlier, when all detergents were powdered, it made sense to have a longer wash cycle to enable the detergent to completely dissolve. I have a very basic washing machine that has two longer wash cycles (18 and 12 minutes) and one short (6 minutes). I find no difference in the cleanliness of clothes washed in the short cycle. I do find that clothes washed a shorter amount of time last longer. I also find it more convenient to wash clothes when it takes a shorter amount of time. There may be some situations where a longer wash cycle is desirable, but these are few and far between.
   Also, with these modern liquid detergents, hot water is really not required. This also saves energy, since normally you must size any water heating system to include clothes washing, probably the second largest use of hot water after bathing and showering.
   If you have a solar energy system it is always most efficient to do clothes washing and drying when there is ample solar energy for electrical and heat generation. This means during peak sunlight hours. Sometimes this may not be convenient. In such cases it is possible to set your washer and dryer on a timer. The laundry is loaded into the washer along with the detergent which is placed in an open plastic cup. When the timer turns the appliance on, the agitation spills the cup of detergent and the wash cycle is started and runs automatically to completion. 
   The use of a dryer is not preferred by some people. They would rather hang their clothes to dry in the sun. This is, of course, a direct use of solar energy and is therefore very cost-effective. But for many it just isn’t practical. Drying clothes in the sun results in the clothes being exposed to air pollution, wind-blown dust, rain, contamination by birds and insects, and the microbes in the environment. It is also much slower, so that clothes drying cannot be completed in the limited time people have available. Also, it has been demonstrated in research that many parasites that survive the washing cycle are killed when subjected to prolonged heating in a dryer.   For these reasons, I believe that using a clothes dryer is the most practical and healthful approach.
   If you choose to utilize a clothes dryer, there are two options, an all-electric dryer or an electric-gas dryer. An all-electric dryer is one of the most energy intensive appliances that a household can utilize. It requires the building of a significantly larger solar-electric energy system. For this reason it is not the first choice.
A gas-electric dryer uses electricity only to turn the spinning drum that holds the clothes. It uses a small fraction of the electricity required by an all-electric dryer. The heat is provided, very efficiently, by the combustion of natural gas or propane. This burning occurs in a flame that operates at atmospheric pressure, by far the cleanest way to create heat from a gaseous fuel. Gas-electric dryers also tend to dry the clothes faster requiring less electricity for turning the drum due to the shorter time interval.
   Another potential advantage of this type of dryer is the possibility of creating a solar heat generating system that can replace some or all of the gas normally used during operation. Heat can be readily stored in black-painted containers of water enclosed in a simple glazed box collector. If this collector box is vented into a closet containing the dryer, the use of gas can be reduced. This occurs automatically because the gas burner turns off whenever the air is at the correct temperature. By supplying pre-heated air to the appliance, the burner ignites the gas less often. The collector must take advantage of the fact that hot air rises. Its opening into the dryer should be higher than the input of air into the collector box. The air input and output should be screened to prevent the entry of insects.
Another approach for this type of hot air solar collector design is to use black-painted copper pipes that are open at both ends. Copper is one of the best metals for absorbing, conducting, and emitting heat. When copper pipes are closely spaced in an angled, south facing glazed collector box, with exposure to light, they rapidly heat up. Because the inside and outside surface of the pipe is exposed to the air, a large surface area is available allowing the heat to be rapidly radiated and convected. In direct sunlight, these pipes very quickly become too hot to touch. By directing this heat into your dryer you can substantially reduce gas usage.
   If you use the vented hot air from the dryer to heat the incoming air by use of a heat exchanger, this will further reduce the energy required. Since a solar heat collector is a form of heat exchanger, you can heat the top of it with solar energy and the bottom with the expelled air from the dryer. Strategies like these can dramatically reduce energy use. I have made one that collects solar heat and uses the waste heat from the dryer, reducing the need for gas.
6. Lighting
Lighting can either be substantially consumptive of electrical energy or use very little at all. This depends on how you provide the lighting that you need.
   Lighting is a fundamental convenience issue. We require an adequate amount of light to be available when we need it, whether day or night.
The best way to get light during the day is from daylight provided by the sun. This can be accomplished by having adequate windows or skylights. There are also solar light tubes that come through the roof. These are not necessarily cost-effective because with efficient electric light bulbs, indoor electric lighting does not have to cost much in terms of energy. Also, any system that penetrates your roof tends to be a place where water leaks can develop.
   New lighting technologies use a fraction of the electrical energy that older incandescent and halogen bulbs use. Any light that becomes too hot to touch is inefficient, as much of the energy is producing heat instead of light. The most widely available, efficient lighting technology is called compact fluorescent (CFL). These spirally wound fluorescent lights use about ¼ the amount of energy used by an incandescent bulb of the same light output.
   They can be used in any normal lamp or lighting fixture and they can last 5-10 years. These are a major component of my lighting system.
   There are two downsides to these types of light. First, they have to warm up for before their full light output is available. I personally, have not found this to be much of a problem. The light comes on with sufficient brightness to accomplish most tasks and quickly attains full brightness.
   The second problem is that they contain a small amount of mercury which is toxic. If you break one of these bulbs a small amount of mercury can be released. However, this is
only the case if you use a compact fluorescent light with an exposed spiral light tube. These lights can also be purchased with an opaque plastic bulb that covers the fragile tube. These are not only more attractive looking but they also capture any gases from the tube if the light should be accidentally broken.

LED Lightbulb

   The latest efficient light technology is LED (Light Emitting Diode) lighting. These small fully electronic light emitters are about the size of a pencil eraser and many of them are grouped in a single bulb. They use a fraction of the energy of a standard incandescent bulb, much less than a compact fluorescent, and they last just about forever. They are rapidly falling in price and may soon overtake compact fluorescent as the light system of choice. The only down side is that they are a very white, pinpoint light source that is not useful for all applications. This is being worked on and new full spectrum LED lights should be available within a few years. This one from Delta is exceptional. At 0°C, the efficiency of this LED lamp is six times higher than a CFL of the same wattage. Lamp life is greater than 35,000hrs, which is six times longer than CFL's and 20 times longer than incandescent lamps. Produced under lead-free conditions, the LED Lamp is also mercury-free.
LED Puck Light

   Right now, the best way to use LED lights is with puck lights. These small battery-powered lights can be mounted on doors, in closets and cabinets. Because they detect ambient light, they can be set to automatically turn on when a cabinet or closet is opened. They use so little energy that 3 AAA batteries can power them for years. They cost about $5 each and are excellent special purpose lighting fixtures. I have one on my bedside table, one lighting my door lock, and I keep one in my car for use as a flashlight. My refrigerator uses a small incandescent bulb that turns on when I open the door. I am planning on using an LED light as a replacement. Over a year this can result in the saving of several kwHrs.
    In development are some even better lighting technologies that should be widely available at reasonable prices within the next few years. These are also fully electronic light-emitters with the added benefit that they are flat, like a sheet of paper. I currently use a type of night-light called electro-luminescent lighting. These  plug directly into the wall and look like a small TV screen with a pale green light. They use a very small amount of energy; about 3 one hundredths (0.03) of a watt per hour. That is so little energy (less than a watt per day) that it is not necessary to turn it off.I have been running a couple of these non-stop for over seven years.
   The new flat lights will have the added benefit of being able to be wall mounted in any shape you can imagine. The world of lighting is about to open up into a major hyper-efficient, creative direction. Such lighting, either capacitive or organic light emitting diode (OLED) should be readily available within 5 years. So, the energy that you use for lighting is going to get smaller and smaller. Invest in the best solution for now. By the time that wears out, even better, more durable and efficient products will be available.

7. Television

Whether broadcast, cable, or video player and monitor, TV is a significant appliance in most people’s homes. Unfortunately, it is also often a big area of energy waste as TV sets are often left running even when there is no one watching. This may not seem like a big deal if you look at it on a daily basis, but when you start to add up the yearly energy costs for an appliance that may be wasting 10% or 15% of its energy, it can be a substantial unnecessary cost. This can be particularly the case when the modern large-screen TV sets are left running without an audience. It pays to give closer attention to the energy requirements of your TV and at the habits you may have developed in regards to its use.
   Television sets have a power-use rating somewhere on the set. It either states the voltage and the amps that the set requires or it gives a kW rating. An approximation of the watt rating can be calculated by multiplying the volts times the amps. When an appliance says 120 watts, for example, that means that 120 watts are used per hour.
   Most televisions have a standby mode. Whenever it is plugged in, even when switched off, it is drawing a small amount of energy. This is for such features as instant-on, a dubious advantage at best. I circumvent this wasted energy by use of switched power strips or by means of electrical receptacles that are controlled by a switch.
   I have a 32 inch LCD television/monitor that uses 55 watts. This is in my living room. I also have a 20 inch LCD TV/Monitor in my bedroom. It uses 60 watts (80 watt rated). In addition to these two, I have a 9 inch widescreen all-in-one DVD player that uses 14 watts. This gives me choices depending on how much energy is available. In my solar energy system, there is never too little to use my 9 inch screen. On dark cloudy days, I might choose my 20 inch TV over my 32 inch because it uses only 2/3 as much electricity.
   There are other ways to reduce energy consumption and still enjoy large screen entertainment systems. New video glasses allow the viewing of a simulated 60” TV screen with a few AA batteries! Plus, you can see through the glasses.
   Energy efficiency advances such as this will decrease our electrical energy requirement for a high standard of living and will result in very small solar energy systems to power our needs. Keeping on top of these kinds of evolving low energy devices will allow the solar energy system that you install now to provide more than enough for your needs going into the future. What will you do with the surplus? How about:
8. Power Tools
My solar energy system easily handles the use of electric power tools. Table saw, chop saw, chain saw, drills, sanders, planers, and compressors are no problem as long as the use is occasional. You might think a power saw uses a lot of energy and that is correct, but it accomplishes its work in a very short time so it uses energy in bursts. This is important to understand. If my table saw is rated at 1.2 kwHr and I use it for 6 minutes (1/10th of an hour) I am actually only using 120 wHr, the same as running my TV for an hour.
   The way I use these tools, the work is generally accomplished very quickly and uses relatively little energy. However, because these tools draw a lot of energy for a short time, it is best not to use them simultaneously with too many other large-drawing pieces of electrical equipment or to keep them running unnecessarily. In my system I could do the wash, run my table saw, but not operate the microwave all at the same time. With a solar powered system, you can overdraw the inverter causing a breaker to open. However, with a sufficiently large inverter or with multiple inverters you can run any combination of loads at the same time. See the section on inverters.

An excellent use for surplus energy is cordless power tools with rechargeable batteries. I use cordless drills, screwdrivers, saws, string trimmer, hedge trimmer, flashlights, and plan to get an electric riding mower!! I also use an electric water distiller to make distilled water for my batteries. It draws  650 watts so is best used when the batteries are fully charged and there is bright sunlight. For this purpose I preheat the water with solar, to minimize the electric draw that would be required to heat the water to a boiling temperature.

9. Desktop Computers; Laptop Computers; Printers/Scanners
Desktop computers use much more power than laptop computers. Typically, a full desktop model has a power supply that draws from 200-300 watts per hour.  The display also uses a substantial amount—up to 200 watts per hour depending on screen type and size. The average home system probably uses about 250 watts per hour with screen and printers/scanners attached.
Desktop Computer

The laptop, on the other hand, uses from 20 watts per hour for a netbook or tablet, to 90 watts per hour for a full sized version with a large (17-20 inch) screen. Clearly a laptop, netbook or tablet computer is much better for your pocketbook and the planet. Average daily computer-use can be 2 hours or more. That is 500 watts for the desktop computer versus 180 watts for a large screen laptop. If you multiply that out for a year, the amount of energy used is substantial and the savings that can be had by using a laptop, netbook or tablet computer are significant.

   Annual Desktop energy usage: 500wHr x 365 days/year = 182.5 kwHr/year
Annual Laptop energy usage:   180wHr x 365 days/year =  65.7 kwHr/year___
Energy Savings by using a laptop 182.5 kwHr – 65.7 kwHr = 116.8 kwHr/year
By reducing your use by 116.8 kwHr/year you require approximately 90 watts less of solar generating capacity. At about $8.00/watt installed, this amounts to $720 less solar generating equipment. This is why efficiency and affordable solar energy systems go hand in hand.
   Of course, many people use their computers much more than 2 hours a day. In this case the saving from using a laptop becomes increasingly dramatic, particularly for those who earn their living with a computer.
   Printers and scanners use much less electricity than computers. For example, my all-in-one Canon printer/copier/scanner uses 22 watts per hour when operating. When it is on but not operational it uses only 3.9 watts per hour. When it is off it still uses .9 watts per hour. So, is it worth it to run the machine through a switched power-strip to save that .9 watt/hour? Let’s do the math:
.9 Wh x 24 hrs/day x 365 days/year = 7,884 Wh/year
Wow, that is a lot of energy use for something that gives us no noticeable benefit!       
   When we calculate the savings from less generating equipment, the power strip pays for itself in about 1½ months. And by the way, if I was using a separate printer, scanner and copier, each one of these would have about the same amount of energy use in the off position. In this case, a power strip pays off even faster!
Now, if we also shop around and purchase the most efficient models we can save even more than the numbers represented by these average computer systems. It pays to shop for efficiency.

10. Microwave; Cooking
  I have a very small microwave oven that I don’t use that often. I use it mostly for re-heating leftovers or thawing frozen bread (when I forget to just take it out of the freezer and put it in the refrigerator). It uses 800 watts per hour. That sounds like a lot, but generally I use it less than 6 minutes at a time, or 800 Wh x 1/10 hour = 80 Wh. As long as I use this appliance and other high-draw appliances with discretion, they do not add that much to my energy requirements.
   If I use my microwave for 6 minutes a day, 6 times a month that results in energy use of 5,760 Wh (5.76 kWh) per year. That is less than the energy wasted when I don’t use a power strip to turn off my printer/copier! Oh, and by the way, your microwave can be turned off with a power strip as well.
   So as you can see there is more to understanding energy use than meets the eye. Other high energy consuming appliances such as toasters, blenders, irons, hair

dryers, etc., are relatively small energy users if they are used occasionally for short periods. Even so, it is advantageous to get the most efficient model that has the features you require. These things add up over time.
   The most energy efficient way to cook is with gas. Electric ranges and ovens are energy hogs. An exception to this may be efficient convection cooking appliances. Conventional resistance-heated electrical cooking appliances have no place in an energy-efficient home. Propane and natural gas are not only superior in terms of the heat control, but actually reduce energy use, because of a more efficient heat transfer. However, some kitchen chores can still be done efficiently with electricity. Immersion heaters for heating water are very efficient since all of the energy is transferred to the water. In the near future new technologies will replace or augment many of the current options available today. In development are a new generation of products that will allow cooking with hydrogen gas created on demand from your solar electricity.

11. Small Electronic Devices (cordless phones, digital cameras, cell phones, etc.) 

These types of electrical uses are no problem with a solar energy system. They actually give you added ways to store energy in functions that you use all the time. Plus, they use durable, efficient hi-tech batteries.
In my solar powered household, I use a rechargeable cordless phone and a rechargeable

vacuum cleaner. The convenience that such appliances provide is worth the small constant energy use. My laptop computer is also always in battery charge mode and uses very little energy when the computer is turned off. I also use rechargeable drills and saws.

The Photovoltaic or PV electrical system

PV panels, shown here, are devices that generate electrical energy from sunlight. They can be made of a variety of materials. The most commonly available are made from silicon (the main ingredient of sand). Such PV panels can be made from pure crystalline silicon or amorphous (mixed crystals) silicon and have an efficiency of 15-22% in converting solar light energy to electricity. Such PV panels are currently made in practical sizes from 100 watt to 300 watt peak output. Most have a 20-25 year factory warranty against degradation in power output. These solid-state (no moving parts) devices, when used appropriately, are among the most durable and low maintenance of any products ever devised by man.

What Kind of System is Best for My Needs?
There are basically two types of PV electrical generating system. One type is capable of feeding electricity back into the power company grid. This is called a grid-tied system. When the PV generated power you collect is more than you require it runs your electrical meter backwards. This is essentially the same as selling your surplus power to the power company at retail price. This type of arrangement is called net metering or feed in tariff (FIT). Some FIT systems utilize two meters. One measures the energy you purchase from the power company and the other measures the energy that you sell to them. A downside to the two meter system is that in many cases you must pay income taxes on the power you sell as well as other federal and state taxes on the power you purchase. This, of course, increases your payback time. There is, however, another approach that does not tax your energy production or use. Sound good?
   This other option is to have an independent system that does not feed power into the grid, but is used directly by you, the owner of the system. Systems like this that maximize autonomy can still be connected to the power company grid, in order to use it as backup when more energy is required than the PV system can provide. In this case, the grid power charges your batteries and powers your household until the sun’s energy is again sufficient. with such a system, properly sized, you can expect to get 98-99% of your electrical energy from the sun.
   There are advantages and disadvantages to each approach. For example, the power company does not have to allow you to hook up a grid-tied system. With a grid-tied system your power goes out when the grid goes out. Also, the time and red tape involved in hooking up a grid-tied system may be substantial and costly.

Answer to Questions about:
Grid-Tied PV
Independent PV System
Does your power stay on in a grid power outage?
Is your equipment protected from spikes and brownouts?
Does the Power Company decide how big a system you can have?
Can the Power Company confiscate some of your power?
Is there excess red tape to install your system?
Are batteries required?
Is it the lowest-maintenance option?
Can there be surplus power?

The power company may confiscate a part of your power output without payment. How does this occur? Most grid-tied system power-purchase agreements allow the power company to zero out your meter at least once each year. Any surplus accumulated is confiscated. This has a perverse consequence. It now becomes in your best economic interest to install a system that will never produce a surplus that can be confiscated. If the meter is zeroed out on January 1, the buildup in your account from the bountiful summer sunshine may be wiped out. Unless you size your system to produce just what you need in the summer months, then the power company is going to get some of the output of your system for free. Otherwise, you would normally size your system to your winter requirements which means you have enough energy year-round. This under-sizing of your solar system results in you having to purchase more energy from the power company in the winter. So you lose either way.
   In my opinion the economic, technical, and reliability issues give an edge to the system that is not grid-tied. Although the non-grid-tied system is somewhat more expensive due to the cost of batteries, it yields great benefits for a modest additional cost.
   The benefits include energy security (no power outages), very clean power (no damages to your appliances and equipment), and complete control of the surplus energy often generated by solar systems. I use this surplus for summertime activities such as creating mulch (fertilizer) from nitrogen-rich yard waste with an electric chipper-shredder as well as running my electric chain saw to provide material to be chipped. It can also be used for air conditioning, food processing, and other seasonal uses.
   While the simple maintenance procedures for battery systems can be done by the average householder, some people may want to use a grid-tied system if they have no practical way to maintain batteries or if they utilize highly variable amounts of electricity. The simplest approach to maintenance is by having a maintenance contract with your installer or another local firm specializing in this work. But some people live in places where such amenities are not available and are unable to perform these procedures themselves. Grid-tied systems make sense for such situations.
How it Works
PV panels generate direct current (DC) electricity, the same type as used in automobiles to power lights, radios, fans, etc. The DC electricity generated with the panels is directed to a charge controller on the way to a battery for storage (except in some grid-tied systems it goes directly to the inverter). The charge controller keeps the energy coming at a rate that will efficiently charge the batteries or operate the inverter. Increasingly charge controllers also document the amount of energy produced and control a number of automated functions for assuring long battery life.

    The most widely available, economical batteries used in a household energy system are called flooded lead-acid batteries. These are a very old technology. Operated properly they are 90% efficient and can last up to 15 years. They have limitations and are relatively expensive per kWh stored, but you only have to store a fraction of the energy that you use. Most of the DC energy is changed to AC for immediate use by the inverter. You only store the energy needed when the sun is not shining. So the batteries are actually not that big an expense in the life of the system unless you use most or all of your energy at night.
   As an example, I paid $1,200 for my batteries that give me 5-10 kWh of storage at 90% efficiency. I expect them to last at least 10 years. That is a cost of about $10 per month. There are new batteries in development with 1/4th the weight, 2 to 3 times longer life, and that could last up to 25 years. They have a claimed 95% throughput efficiency and are completely no-maintenance and environmentally friendly. By the time your first set of completely recyclable, lead-acid batteries is used up, these new types should be available. 
   From the charge controller, DC electricity can power loads that can use DC directly. There are some tools and appliances from the recreational vehicle and boat industry that use DC, but they are generally not as durable or high quality as regular AC (alternating current) household appliances. The appliances made to use household AC electricity are mass produced in huge volumes and are therefore more affordable. They also have much larger research and development budgets behind them. DC appliances just can’t compete. Although a bit of energy is saved by using DC, the low quality of the appliances and their short life expectancy is not worth the savings of energy.
   Standard household appliances use alternating current (AC) which is electrical energy that oscillates in a wave pattern. In a PV energy system, in order to utilize standard household appliances and tools, the DC is changed to AC by means of an electronic device called an inverter. The inverter conditions the DC to replicate the sine-wave characteristics of the AC that is available from the power company grid. If the inverter can also be synchronized and attached to the grid, it is called a grid-tied inverter. This allows the homeowner to sell surplus power to the power company. Usually this happens by making the electric meter turn backwards. There are a few advantages to this, as shown in the previous table, but many problems.
In addition to these main components there are a variety of junction boxes, breaker boxes, power disconnects, and instrumentation displays.

The Energy Available from the Sun
With the coming of daylight, PV panels start to generate DC electricity. At first, very little is generated. Then as the sun rises higher in the sky the amount of light energy falling on the panels increases and so does the output of the panels.
Here is a typical chart of the amount of solar radiation over the course of a sunny day.
 As you can see here, 90% of the energy falls between 9:00 AM and 4:00 PM on a clear day with the peak amount being available at noon. Of course, nature is rarely this simple due to clouds, haze, fog, etc. However, this graph does represent a useful baseline. It shows us, for example, that if we want our solar panels to track the sun, we can ignore the time before 9:00 AM and after 4:00 PM. It also shows that we capture most of our energy in about seven out of the twelve or more hours of daylight.   

The chart shows the typical annual variation of solar energy at several different latitudes.
   The daily amount of energy also varies over the course of the year since the length of the day is shortest on December 21 and longest on June 21.
   If we look at the green line on this chart, representing the yearly solar energy variation at 30 degrees north latitude (Jacksonville, Florida), you can see that the amount in December is about half the amount of energy available in June.
On the red line at 60 degrees latitude (approx. at Anchorage, Alaska), we see that there is only 1/14th the amount of energy in December as there is in June. That is quite a striking difference. In order to be a practical and affordable year-round energy source, solar energy systems must be sized according to what the user requires in the winter when the least amount is available. That means that wherever you are, there will be a substantial surplus of electricity in the summer. This fits well with needs for air conditioning. In independent systems you can also use this summertime surplus for electric powered yard tools like electric lawn mowers and chipper-shredders (yes, they are available). In grid-tied systems this surplus turns your meter backwards.
   As a result of the summer surpluses, the further south you are the less expensive your solar energy system needs to be because (as you can see by the blue line on the chart) at the equator there is a very high amount of solar energy throughout the year. In other words, the further south you go, the smaller a system you require to provide your year-round energy needs. Due to these factors, solar energy is a practical alternative from the equator to about 50 degrees latitude (Seattle, Washington). However, the further toward the poles (north or south) you go, the more your system will cost because you will need more PV panels. This also means a higher installation cost.
   Of course, these average solar energy figures are only an approximation due to variations in weather that can obstruct the sun. Fortunately, PV panels continue to generate electricity in any light. Blue sky or scattered white clouds is the best. Scattered white clouds can actually reflect additional light onto the panels providing more usable solar rays than would be available from a clear blue sky. As a result, even if such white clouds periodically block the sun, they can yield the same average energy or greater than the amount from a perfectly clear sky. Light grey clouds will reduce the output to 50-60% of the peak rating. Dark grey clouds can reduce the output to 10-15% of the rated output. This is why all cost-effective solar powered systems utilize a backup source of power. It can come from the grid of the power company, a generator, or alternative energy generators such as wind or hydropower. However, the amount of energy that you will need from these backup sources will normally be small and therefore, not costly. I use a Honda generator. My goal is to power it with hydrogen generated with my surplus summer sun energy.

Photovoltaic (PV) Panels
   PV panels, as previously mentioned, come in a variety of sizes, materials, and configurations. For the sake of brevity, we are only going to consider the most commonly available type: crystalline or multi-crystalline silicon that come with a 20-25 year warranty. These panels are always UL approved for safety and because there are many firms making and selling them, they are competitively priced and always available.This Web site keeps track of the current retail market prices for silicon PV panels.
   PV panels are sized to their peak output capacity. On a clear day at noon, if the panel is perpendicular to the sun’s rays, it should put out an amount in watts that is very close to the rated output of the panel. Of course, this is an approximation, but it gives you a starting point for designing your system. You can get actual current prices at

   Most panels are made up of an array of individual solar cells that are connected together in a particular configuration to give panels with a certain output in volts, amps, and watts.

   These panels are generally enclosed in an anodized aluminum frame that is about 1½ inches thick. The PV cells themselves are behind a piece of shatter-resistant glass and encased in a clear silicone-rubber type of material. An anti-reflective coating is employed to minimize the light being reflected away. The individual cells of the panel are connected together by very narrow, flat metallic conductors that can be seen under the glass. The cells are connected at the factory to make a range of possible voltages, with 6, 12, 24,and 48 volts being the most common.
   On the back of the panel, the cells are protected by a synthetic plastic material that is rubber-like and has a white smooth surface. Also on the back can be found the junction boxes where wires are connected to take the DC electricity to the charge controller. These are designed to be very durable and weather-proof. Some panels have special wires with weather-proof connectors and others have junction boxes with screw terminals.
Panels can be purchased in many different power output sizes from 15 watt to 300 watts and larger. The smaller the panel, the higher the cost for connections (you need more connections for the same amount of power). The larger the panel, the heavier it is and the more unwieldy to work with. In my experience 120–240 watt panels are the best balance. I prefer the 120 watt range for practical reasons. Should you ever have a panel failure, you will be losing a smaller percentage of your generating capacity while waiting for your replacement from the manufacturer (nice to have those 20-25 year warranties).
   Speaking of warranties, this is a very important issue. The warranty is only a strong as the company that provides it. If the company goes out of business in the 25 year period, your warranty disappears. That is why I strongly recommend only using well established, large firms who will be in the business of manufacturing these panels long into the future. These include Sharp and Kyocera, two of the strongest Japanese manufacturers. New companies such as Sunpower may have more risk. Chinese manufacturers seem to have very weak warranties when you read the fine print. So remember price is not everything. Purchasing from a solid company with a reputation for backing up its products is the best investment.
I recently helped a friend replace two defective Kyocera panels that were ten years old. Kyocera not only paid for the shipping cost of the new panels, but also the cost to return the old ones. They also paid for the labor to swap the new panels for the defective ones. Now, that is a warranty that has value—no arguments, no hassles. Kyocera knows that replacing the very few panels that fail is the best advertising they can buy. And they are right!
There are three general approaches to mounting the panels:
On the roof at a fixed angle
On a ground mounted structure at a fixed angle
On a ground mounted structure capable of tracking the sun in one or two axes
    Two axis tracking systems can yield up to 50% more energy with the same panels as do fixed mounting systems. But there is a catch.
   Tracking systems are mechanical and have a much shorter life than the PV panels. They require quite a bit of maintenance. To track the sun, the panels will necessarily be exposed to occasionally powerful winds and corrosive components of the atmosphere that can destroy the mechanical parts of the installation. If the tracking system is made out of very large gauge stainless or enameled steel and sunk into 6 feet of concrete, it may withstand the wind and corrosion. But then the expense of the tracker is more costly and will cost more than adding 50% more fixed panels.
   In my opinion, the durability, economics, and maintenance issues always give the fixed mount panels an edge. In places where there is no wind, rain, or corrosive elements in the air, tracking systems might be worthy of consideration. I have not encountered such a situation in real life.
   Whatever type of mounting system is used the panels must face south and have little or no shadows from trees, other buildings, or structures, including other panels, during the peak sun hours (9:00 AM – 4:00 PM). They should be mounted at an angle (the optimal mounting angle is addressed in the article on page 95 included in the Appendix) that balances the amount of energy generation, structural durability, and access for maintenance. This last recommendation is a very important consideration.
   Despite the incredible ruggedness of PV panels, over the course of 20, 30, or more years, other maintenance issues can arise. A squirrel chews a wire. Nearby lightning damages a panel. There will eventually be something that needs attention. If the panels are mounted in a way that makes it difficult to access them, that is an unnecessary long-term cost and inconvenience.
   This means there should be space around the panels so that you don’t have to dismount a bunch of them to reach another one. It also means that there should be a type of mounting that allows easy access to the wiring box mounted under the panel. This is where you check the individual performance of the panels when diagnosing problems. 
   Panels should have a system of circuit breakers with LED lights that go on if a breaker is tripped. LED lights are readily available for this purpose. These LEDs should be mounted in a very visible location, like the kitchen, so that any problem will be quickly noticed. It is also useful to have electrical test points that are conveniently located, in order to quickly diagnose any problem with the panels. The best place for this is at the breaker box which should be easy to access. Each panel should have its own breaker, so that troubleshooting is simple. Panels of DC circuit breakers are available from marine electrical suppliers. These are very convenient to install and use.

Mounting panels in large fixed fields like the house pictured above is not advisable. How would you clean the panels on this house? Not easily. Even if you build in access to the wiring from the underside of the panels, you will have a heck of a time doing periodic cleaning of the panels. It may look cool, but it is not practical.
PV panels should be periodically cleaned with a soft broom and sprayed with water to remove built-up dust, pollution, animal droppings, leaves, pollen, algae, mildew, etc. All of these things can significantly reduce the energy output of the panels. Do not use solvents or detergents to clean panels as some are capable of damaging anti-reflective coatings on the glass.
   As for roof mounting, you are better off with something like this than the example from the previous page. Why? Because of easy access for cleaning and maintenance.
   Generally, the best installation for ease of maintenance is a ground mounted array. A sturdy, painted wooden frame made of construction grade 4x4 and 2x4 lumber that is mounted to deeply-buried concrete piers is a very cost effective approach. It can even be hinged for making seasonal adjustments that can yield an additional 4% or 5% of electricity.
   Properly prepared treated lumber (rough-sanded, primed, and painted) can easily last a lifetime with minimal maintenance. Use heavy metal brackets to lift the legs of the installation off of the concrete and soak the bottoms of the uprights with an anti-fungal mildewcide and pesticide before painting so there will be no rot or insect damage.
   An additional advantage of wood is that is does not corrode when placed next to the metal frames of the PV panels. If you use stainless steel fasteners and anti-seize compound, you get an extremely durable and cost-effective installation that can be easily maintained.

Integrated Photovoltaic Installation
Another approach to panel mounting is to create an integrated installation where all of your panels, batteries, electronics, and electrical breakers and disconnects are all a part of a single installation. There are significantly lower costs when all components are placed together. Less wire, smaller wire size, fewer materials for enclosing batteries, inverters, etc., and ease of maintenance. The final output of 120/240 volt AC can be run to the house in underground plastic conduit for 125 feet or so for a neat installation. As illustrated here, a weather-proof, wooden closet can be built underneath a ground-mounted panel structure. The closet can have compartments to hold inverters, charge controllers, batteries, and breaker boxes, and disconnects. Even a backup generator can be placed here for those who are not connected to the grid. This puts all of the equipment together. It is safer, cheaper, and more durable than any other approach. The installation can be carefully landscaped to reduce its visual impact.

Wiring the PV Panels
As was mentioned earlier, panels can come from the factory wired for 6, 12, 24, or 48 volt DC. So how do you decide which voltage to use in your system? The panels are priced per watt, so a higher voltage gives lower current but results in the same amount of watts (power) per dollar.
   The reason that panels are sometimes connected in series to get higher voltages is because higher voltages require a smaller, less expensive wire size. This can be quite important if the PV panels are a long distance from the electronic controllers, inverters, and batteries. However, if the panels can be mounted near to these components, then wire size is not an important cost issue. There are many reasons to mount the components close together, including ease of maintenance, ease of troubleshooting, lower-cost installation, less wire and conduit, etc. This is simply the smartest way to design a system.

   There are also a number of advantages to using a lower voltage. In particular, 12 volt DC systems have some economic and practical advantages that no other system voltage can claim.
·          Automotive instrumentation can be used to monitor your system. Because there is so much of this stuff made it is very inexpensive and durable.
·          Batteries connected to make 12 volt systems can require less complex interconnects and can be cost-effectively mounted in a single row which makes maintenance a snap. Batteries have to have distilled water periodically added through caps in the top of the battery. Easy access makes this process quick and painless. 
·          Fewer batteries are needed since most of the heavy-duty deep cycle batteries of this type come in 2, 4 or 6 volt cells. Fewer batteries means less cost.
·          Fewer batteries = less to go wrong. If any cell in a battery bank goes bad, it effects the entire bank. Batteries that are connected in series to build voltage can develop thermal runaway from defective cells.
·          Industrial 12 volt battery chargers that can rapidly charge a large bank of batteries from your backup source are available for low cost. Fast chargers with higher voltages are much more expensive.
   12 volt inverters are available in sizes of 2.8 kW of power with 6-9 kW of momentary surge capability. This is enough to power a typical 4 person household (2 adults, 2 children) or any smaller household. More than 4 people require a larger inverter of 3500 watts or more and these are generally available in 24 or 48 volt versions. However, there are also 12 volt inverters that can be connected together to run in parallel. Two 2400 watt inverters connected this way give a 5000 watt output.
   My advice is to stick to 12 volt systems and design the system to place all of the components close together. I have made this choice for the past 26 years and have never been sorry. I have seen many people with 24 and 48 volt systems develop expensive battery problems in addition to the higher initial cost of batteries. 

Wiring Protection
Wires that go from the panels to the charge controller must be protected from the elements (sun, rain, air pollution) and the chewing of insects and small animals. There are a variety of types of flexible conduit available for this purpose.
   These conduits are generally made of plastics that are UV resistant and corrosion-proof. The conduit will generally be in the shadow of the panel. This protects it from the sun and rain to a large extent. But the sun moves across wide angles and the rain can be wind-driven, so this extra protection is warranted. I recommend caulking the conduits at each end, after the wires have been installed, to prevent ants and bees from nesting in them or using them for access to your junction boxes (I have seen this occur on more than one occasion). The best conduits to use are approved by the NEC (National Electrical Code).

Wire Size
Determining the wire size to use in various interconnections within your system can be determined by using the technical information in the Appendix (Pg. 11) concerning wiring size and amp capacity. These are very important issues. Losses from inadequately sized wiring can be substantial. You must always use adequate wire sizes to insure the maximal flow of electricity.
You can also find wire size calculators on the Internet.
Just write the lengths and voltages in the boxes and your wire size will be calculated.
Color-Coding and Wire Type
AC and DC circuits should always be color-coded for safety reasons. Anyone working on, repairing, modifying, or maintaining an electrical system needs to know what type of electricity is in the wire. This is best accomplished by a consistent application of color-coding the wires.

   Wires made for AC, also called Romex, consist of three or four individual wires made of a single strand of copper with insulation of different colors and are enclosed in a single-sheath of white or yellow insulation. The hot wire is black, the neutral or return wire is white, and the ground wire is bare copper or green insulated. In the case of a four-wire cable for certain applications there is also a red wire. It is not advisable to use this AC wire for DC circuits. The single stranded AC wire has more resistance than the same sized multi-strand wire typically used for DC applications.
   Wires that are appropriate for DC circuits are multi-strands of copper encased in Red or Black insulation. The red is for wires that originate at plus (+) or positive connections. The black is for wires that originate at minus (–) or negative connections.

   Special solar panel wire with black and red insulated wires in a very rugged outer casing is also available. I have used it and can recommend it as it saves the cost of conduit.
   In some cases where combinations of series and parallel connections are made, it is not possible to always follow this red and black wiring scheme. In that case, the wire should be wrapped with electrical tape of the appropriate color at the connection. This is both a safety and maintenance consideration. Accidental mis-identification of wiring sources can cause injury or inadvertent destruction of tools and equipment.

Charge Controllers
The charge controller is an electronic device that regulates the energy that is coming from the PV panels and going to the inverter and/or batteries. Technically, there are many approaches to accomplishing this. For the end user, the important things to know are the:
·          reputation of the manufacturer
·          efficiency of the controller
·          warranty provided by the manufacturer
·          instrumentation that tells you how much energy is being generated and used
·          automating of all functions and stages of battery charging
·          presence of fault alarms and diagnostics
·          programmability of the controller

   Generally, the longer a manufacturer has been around, the more you can trust them. Names such as Xantrex (this includes Trace who was bought by them), Morningstar, Outback, and a few others are fixtures in this industry and provide reliable products with good customer service.
   There are several approaches to charge control. These are Pulse Width Modulation (PWM), Maximum Power Point Tracking (MPPT), and in some cases power diversion when the batteries are full. The older charge controllers, simply turned the panels on or off according to the battery voltage and capacity.See the descriptive technical articles in the Appendix (Pg. 105,107, & 109).
   You can simply connect the PV panels directly to the battery or inverter.  This is not advisable, however, due to over-voltage conditions, over-heating, shortened battery life, and decreased battery capacity. The investment in a charge controller is well worth the savings in battery life and capacity.

    As a result of the deficiencies of the older on-off devices, a class of charge controllers using Pulse Width Modulation (PWM) were developed that give an optimal charging regime for the deep cycle batteries used in solar applications. Highly efficient and very low cost per watt of controlled power, these have become very sophisticated and usually include volt, amp, and accumulating kWh metering.
The Maximum Power Point Tracking (MPPT) charge controller differs in that it calculates the voltage at which the module is able to produce maximum power. The MPPT system then operates the PV modules to extract the full wattage, regardless of present battery voltage. A high efficiency DC-to-DC power converter converts the module voltage at the controller input to the appropriate battery voltage at the output.
With MPPT, if the whole system—wiring and all—was 100% efficient, a charge current increase of 42% would be achieved by harvesting module power that would have been left behind by a conventional controller. But nothing is 100% efficient and actual charge current increase will be somewhat lower as some power is lost in wiring, fuses, circuit breakers, and in the charge controller itself.
   Actual charge current increases from MPPT controllers vary with operating conditions. The greater the difference between the PV module maximum power voltage and the battery voltage, the greater the charge current increase from an MPPT controller will be.
   Cooler PV module cell temperatures tend to produce a greater charge current increase. A highly discharged battery will also increase charge current since battery voltage is lower and output to the battery during MPPT could be thought of as being “constant power.”
   What can be expected of MPPT controllers in cool temperatures with typical battery conditions is a charge current increase of between 10–25%. Cooler temperatures and highly discharged batteries can produce increases in excess of 30%.
   Customers in cold climates have reported charge current increases in excess of 40%. What this means is that in colder climates, current increase tends to be greatest when it is needed most; in cooler conditions when days are short, the sun is low on the horizon and batteries may be more highly discharged. In conditions where extra power is not available (highly charged battery and hot PV modules) a MPPT charge controller will perform as a conventional PWM type controller.
However, an important caveat is that MPPT charge controllers tend to be a lot more expensive than PWM controllers. For example, an Outback 60 amp MPPT charge controller with a 2 year warranty costs around $490.00 plus shipping. A Morningstar 60 amp PWM charge controller with a 5 year warranty costs $200 plus shipping.
   So, the advantage of MPPT controllers in warmer climates may not be worth the extra cost. If you have a 1200 watt system on a fixed tilt, it will put out around 60 amps peak output at 12 volts. The MPPT may give you less than a 10% gain or less than 120 watts advantage and only part of the time. The $300 extra that you pay for the MPPT controller could purchase you an additional 70 watts of PV panels which have a 25 year warranty. The MPPT controller only has a 2 year warranty (5 year extended warranty costs extra). I would go for the extra generating capacity and use the lower cost charge controller.
It is also important to note that if you have more than a 60 amp output with your PV panels, then you will have to run more than one charge controller.
Charge controllers sometimes have the added function of diverting the power to a second use when the batteries are fully charged. This use could be water heating or charging a secondary battery bank. If the secondary battery bank is charged two volts higher than the primary one, then this power can later be dumped into the main battery when it is no longer fully charged. This diversion function helps you to utilize your surpluses rather than simply turning the panels off which is the response that the charge controller would normally have to fully charged batteries.

As mentioned previously, the only widely-available, cost-effective solution for storing electrical energy at this time is flooded lead-acid batteries. These are a special kind of deep-cycle battery, but closely related to the battery that you have in your car. The main difference is that these batteries, being made to store a lot of energy, are much larger and much more durable since they can have many deep discharges before wearing out.
   They are not the perfect solution because they require periodic maintenance (every 30-90 days), which means adding distilled water to the individual cells. (Distilled water is available in supermarkets and hardware stores in one gallon bottles.) This does not sound too complicated, and it’s not. However, because the batteries have a solution of sulphuric acid in them the maintenance procedure must be performed with caution. It is possible for drops of the acid to find their way onto clothing and skin. Therefore, protective clothing and a facemask should be worn if you need to perform this maintenance. This is a procedure that should be performed by a knowledgeable adult.
   Topping up the batteries is easily accomplished with a battery filler that is available at most automotive parts stores. It looks like this:
It has the advantage that when the battery is filled to the proper level the water automatically stops coming out.
    As previously mentioned, always use protective eye gear, gloves, and old expendable clothing when topping up or cleaning the batteries. Should any battery fluid get on your clothes or skin, rinse it immediately with lots of water. Any spills on clothing or the floor should be neutralized with a solution of baking soda and water. A solution of one teaspoon of baking soda per gallon is good to have on hand. Make sure it is labeled so that no one accidentally puts it in the battery!!! In the unlikely event that acid gets in the eyes, flush the eye under clean running water. If this is done immediately there is usually little damage other than perhaps some redness. Make sure the water pressure is not too high as that from a hose nozzle. In an emergency, a hose is OK to wash the eye but remove the nozzle and set it at a low pressure output.

Should the batteries for any reason be over-filled, the excess should be removed with a hydrometer (photo on left) and either distributed to other cells or stored for
later use in a glass or plastic container that is impervious to the acid. A hydrometer is an inexpensive device used to test individual battery cells for their state of charge.
   That said, there are special pieces of equipment that can reduce or automate this battery watering.

Special battery caps called Hydro Caps recombine the gases that are released during battery charging and this reconverted water drains back into the battery. The downside of these is that they must be removed during an equalization charge which is often started automatically by the charge controller. If you are not around when this occurs, it is not possible to remove the caps and pressure can build in the battery. I do not recommend these.

There are also automatic battery-watering systems. These can be purchased for less than $20 per cell, plus (1) $50 indicator module (installed).
The benefits are:
·           Watering takes just a few minutes.
·           No user contact with the battery or vent caps.
·           No safety equipment required (such as eye wash systems and protective gear).
·           Accidental overfilling, acid overflow, and corrosion are eliminated.
·           Achieve the maximum number of cycles for the battery.
·           Optional water level indicator light further reduces maintenance and allows operators and management to easily monitor battery water levels at a glance.
 Battery Types
 Deep-cycle lead-acid batteries are much larger than the battery in your car and weigh much more. There are two main types that are used in solar electric systems. 
L-16 Battery

  The most common type is the L-16 type which is a 3 cell, 6 volt battery shown on the right. Do not substitute the cheaper, smaller golf cart batteries, which are a poor choice for a solar energy system because they have an expected life of only five years or so and are more expensive in the long run.

Heavy-Duty 2 Volt
   The other common type of battery for solar energy systems is the single, 2 volt cell, shown on the left, which is generally employed for the largest systems.

   There are also 2 cell, 4 volt units available in large energy capacity.
These cell/units are connected together into a bank of batteries that will have the voltage required and the storage of kWh needed for the system design. Typical system voltages are 12, 24, and 48.
With these units weighing from 120-150 pounds each, it is fortunate that once installed they will not have to be moved again for 10-20 years. That is, if you install, operate, and maintain them properly. These types of batteries generally have a long warranty of 7-15 years. However, just like any warranted product there is some small risk of failure. That is why installing the batteries correctly is imperative. If one segment of your battery bank fails, you should only have to remove that segment. If you build your battery bank as a matrix of batteries it increases the difficulty in maintaining them and replacing defective sections.
   Don’t build your battery bank like this one. This system went bad after seven years because the batteries were too tightly packed and the internal cells in the matrix over-heated and damaged the case which started leaking battery acid. Then the entire battery bank had to be disassembled in order to remove the damaged units. Not such an easy job considering that the individual batteries each weigh 130 pounds. The battery bank was built into a tightly fitted plywood box, making the job even more problematic. 
   The point is, you must design your battery system and every other part of your energy system with the understanding that over the 20-40 year life of the system there will be maintenance, repair, and upgrading. Make sure that your system is put together in a way that makes accomplishing these things fast and cost-effective. With batteries, that means there must be space around each unit (accessible from all sides) of at least ½ inch; they should preferably be connected in no more than 2 rows (one row is best); and the battery enclosure should be large enough to comfortably access each cell for maintenance and replacement if necessary. Another mistake is to package the batteries in units that are simply too heavy to deal with. Installations like this one below may look good, but in the event of a problem they are a nightmare since it would take a crane to lift them.
Battery Cells in Steel Cases
   These two packages are made of 6 individual, 2 volt cells tightly packed into a steel enclosure. Within a relatively short time, these individual cells will become bonded to each other making it impossible to take the unit apart. When it comes time to replace the battery, it will be nearly impossible to handle without special heavy-lifting equipment. If the batteries have been installed in a tight box, it too, will have to be taken apart. 

The Best Way To Lay Out Batteries
   The best way to layout batteries is in a single row. This allows easy access for maintenance and periodic cleaning. This cleaning is important. These batteries have a slow rate of self-discharge (3% per month). However, this can increase to unacceptable levels if the tops of the batteries become covered with dust which is then contaminated with battery acid. This happens by a force called capillary action and is impossible to prevent. The tops of the batteries should be cleaned with a disposable rag and clean water and then dried completely with another clean cloth. This can be done every 1–6 months depending on how much dust there is in your environment. The batteries are best enclosed in a ventilated, screened enclosure to limit dirt, dust, and insects from contaminating your system.
   I recommend mounting the batteries on a base made of 2x12 construction lumber to prevent them from having contact with the ground which could increase the self-discharge of the battery bank. In any case, do not bury the batteries in the earth or place them on uninsulated concrete.
   If you are in a cold climate, it is best to install batteries in an insulated environment and then use special venting caps and tubes to vent the battery gases to the outdoors. When venting the batteries to the outside, an anti-flashback valve should be in the line to prevent battery explosions.
   A single row layout also eases access to the filler caps or the automated battery filling system which may also need periodic maintenance or repair. Make sure that these functional requirements are simplified by the way you install the batteries. If you don’t, you may end up saying that renewable energy doesn’t work or is not practical. But poorly designed or conceived systems of any type can lead to this result. Don’t let it happen to you. The small amount of attention given to system design yields benefits far beyond the costs.
   The heavy gauge cables that interconnect individual batteries are best supplied by the firm that supplies the batteries. Once you know the layout configuration for the batteries and the system voltage these cables can be custom made for you at a reasonable cost.
   When you interconnect the batteries with these cables, always use stainless steel nuts, bolts, and washers. Apply a light coat of anti-seize compound to the surfaces that touch (cable terminals and battery posts). Anti-seize compound is a mixture of grease and powdered zinc that is available at automotive parts stores.
   Using this product prevents corrosion and assures electrical conductivity. These connections should be disconnected, cleaned, and reinstalled with anti-seize compound every 5-7 years. Following these procedures is necessary to insure a trouble-free battery.
   Always make sure all equipment is turned off and then disconnected before performing this battery terminal maintenance. Use insulated tools to prevent sparks and short circuits and wear protective clothing to avoid injury.

Battery Charging Efficiency
This is an important topic. The amount of energy available from your batteries in both the short-term and over the life of the system is directly associated with charging efficiency.
   A test procedure was developed at Sandia National Laboratories to allow the examination of battery charge efficiency in relation to the battery’s state of charge (how full it is). The results of the study agree well with established understanding that the charge efficiency of flooded lead-acid batteries declines with increasing state-of-charge (SOC), and that charge efficiency is related to state-of-charge in a non-linear way.
These tests indicate that from about 10% SOC to 84% SOC the average overall battery charging efficiency is over 90%. On the other hand, the battery charging efficiency from 79% to 84% is only 55%. At 90% of charge and above, the charging was less than 50% efficient. Electrical energy lost to inefficiency in charging is converted to heat instead of electricity. This heat tends to reduce the life of the battery electrodes by warping and buckling them. It also intensifies the chemical reactions leading to the shedding of electrode plate material. All of these things shorten the life of the battery system.
   This is particularly significant in PV systems where the designer expects the batteries to normally operate at above 80% of battery capacity, with deeper discharge only occurring during periods of extended bad weather. In this scenario, the low charge efficiency at high SOC may result in a substantial reduction in actual available stored energy because nearly half the available energy generated from the PV is making heat instead of charging the battery.
   This problem can complicate the sizing of the battery bank and lead to reduction of capacity and premature failure. During normal weather, this capacity degradation will not be evident, but it will reveal itself when the battery is called on to provide the full-rated capacity, which will be found to be unavailable.
   Extended operation in a low SOC environment can also result in permanent loss of capacity from sulfation (sulfate deposits on the electrodes) if the battery is operated for long periods of time without a sufficient recovery or equalizing charge. When the batteries are sulfated (a sulfur compound coats the electrodes) the only remedy is a long period of charging which aids in softening and removing the hardened sulfation from the electrodes of the battery. This is called an equalizing charge. Charging a sulfated battery is also very inefficient, creating more undesirable heating and battery degradation.
   The impact of low charge efficiency at high states of charge has the greatest potential impact on systems where high energy availability is needed. Such systems usually utilize large batteries to ensure energy availability during the longest stretches of bad weather. This may not provide the energy required if the PV array is insufficient to provide a recovery charge for batteries at 90% SOC and above, where charge efficiency is very low. Charge efficiencies at 90% SOC and greater were measured at less than 50% for the battery tested at Sandia, requiring a PV array that supplies more than twice the energy that the load consumes for a full recovery charge. Many batteries in PV systems never reach a full state of charge, resulting in a slow battery capacity-loss from stratification of the electrolyte and sulfation of the battery electrodes over the life of the battery.
   Actual charge efficiency varies depending upon the rate of discharge, the temperature, and the pattern of battery use. It is something that can only be measured for a specific discharge and recharge cycle. If you change the discharge loads, their duration of use, or the charge rate, the "charge efficiency" will come out different every time. It is perfectly possible to run 2 consecutive discharge/recharge cycles on the same set of batteries and get results of 20% in one cycle and 90% in the other. "Charge efficiency" is directly linked to how the power is removed and returned to the battery and the temperature.
   Because of the difficulty of determining the actual in/out efficiency, it is generally ignored except when the original purchase of the batteries is made. In any case, what the user can do is limited to testing the charged battery with a hydrometer to see that the individual battery cells are within a narrow range of specific gravity, a number that measures the concentration of the acid.
   Temperature has a significant effect on the amount of energy a battery can store. The colder the temperature of the battery the less efficient it is and the less capacity it can deliver. In cold climates it is best to keep your batteries in a heated enclosure. The batteries themselves produce some heat when charging, so a very well insulated enclosure may suffice.
The chart shows the approximate state of charge, voltages, and specific gravity as measured by a hydrometer ( when the deep cycle battery is in a rest state) 
 Battery Durability
As shown in the chart, the number of cycles (assuming one cycle per day) and the life of the battery is maximized by using less than the full discharge capacity. This chart is just an example; different batteries do not necessarily perform the same. Large deep-cycle solar batteries can last for many more cycles if only partially discharged. I try to keep my battery use between 10% and 60% depth of discharge (D.O.D.) in order to maximize durability and lower the lifetime cost. D.O.D. and S.O.C. are the opposite ways of saying the same thing. In S.O.C. terms I run my batteries between 40% and 90% full except for occasional equalization charges.
Because of these efficiency issues, matching the battery size to the amount of solar electrical energy available is critical in assuring an economical, cost-effective system.
   Since the amount of sun can vary widely due to weather variability, the only affordable approach to make sure that you always have enough energy is through the incorporation of a back-up generator. This can be the utility grid (which is usually the most cost-effective) or a free-standing fuel-powered generator. This allows you to be able to assure, under any circumstances, the operation of your batteries in the most efficient way, resulting in the longest life and the highest efficiency. I am working on a plan to use summer energy surpluses to generate fuel to run my back-up generator which is utilized, on average, about 25 hours (5 hours per month) during the winter months . That requires about 16 gallons of fuel, which can be gasoline, ethanol, hydrogen, or a mixture.
   As previously said, I generally run my batteries from 40% to 90% S.O.C except for equalizing charges. This means that at rest, the voltage would be between 12.1 and 12.6 volts. When the batteries are charging they go higher than this. When they get down to an even 12 volts, I would charge them from a backup generator, if necessary, to preserve the life of the battery bank.
   Equalizing charges are an important battery life-extending procedure that usually can be programmed into your charge controller to take place automatically. In solar systems equalization is particularly critical. Why? As your battery discharges, sulfuric acid is consumed. Soft lead sulfate crystals form on the battery’s electrode plates. If the battery remains in a partially discharged condition these soft crystals harden. This is called lead sulfation which over time causes the crystals to become increasingly hardened and more difficult to return to soft active materials during recharging. This actually reduces the capacity of your battery and makes recharging less efficient than it would be with soft lead sulfate crystals.
   According to Morningstar Corp., a leading supplier of charge controllers, “sulfation from chronic undercharging of the battery is the leading cause of battery failure in solar systems. In addition to reducing battery capacity, sulfate build-up is the most common cause of buckling plates and cracked grids. Deep cycle batteries are particularly susceptible to lead sulfation. Normal charging of the battery can convert the sulfate back to the active soft material if the battery is fully charged. However, a solar battery is seldom completely recharged, so the soft lead sulfate crystals harden over a period of time. Only a long controlled overcharge, or equalization, at higher voltage can reverse the hardening sulfate crystals.”
   Equalization also has the benefit of bringing the voltage of each cell to the same voltage which reduces heating in cells that would otherwise have unequal voltages. Heating is wasted energy; something to be avoided!
   Equalization also causes the electrolyte, which sometimes can become stratified in layers of different acidity, to be mixed. Stratification results in the acid settling toward the bottom of the battery where it can corrode the bottom part of the plates and shorten the life of the battery. The rising gas bubbles created by a controlled equalization overcharge actually mixes the electrolyte. This mixing is good.
   Equalization charging can be overdone, however. Too much can cause heating and damage to the battery. That is why it is usually left to the automatic program of the charge controller which initiates a unique equalization charge for different types and sizes of batteries. Equalization can also be performed through the program of most inverter/chargers. But to do this requires the use of your backup generator or the grid, which of course involves a cost for fuel or electricity. Since an equalization charge can last as much as  6-10 hours it can be a significant cost to equalize using a backup generator. I would only do this as a last resort. In 27 years, I have only needed to do this twice.

Monitoring the System
In order to monitor the DC voltage of my battery/photovoltaic system, I use an LED (3/4 inch high digits) volt meter that shows 2 digits to the right of the decimal point, which is hundredths of a volt. Being able to see this degree of change is vital for monitoring the condition of your system at a glance. Seeing only one digit to the right of the decimal point is insufficient to register a change if you turn on a light or other small appliance. Becoming accustomed to how much the volt meter changes with specific appliances allows you to spot problems while they are still small. If any appliance starts using excessive energy because of a defect, you want to know about it so it cannot drain your batteries.
   LED meters are always illuminated, can be easily read day or night at a distance, and use very little energy. If you have a system based on 12 volts, you can purchase such meters for less than $20.00 and wire it directly into your system. Higher voltage meters of this type are more expensive and the meters also need to have a separate lower voltage power supply. 
    So it all sounds very complicated, but in fact it is not. If you maintain your batteries above 12 volts (or 24/48 volts depending on system design) and utilize modern efficient charge controllers and battery chargers, these issues pretty much take care of themselves. A digital voltmeter with a single readout on the wall in the kitchen is all you need to keep track of this. When you turn on a light or appliance the number will go down. When you turn it off the number will go up. These changes are particularly accurate indicators at night when the batteries are not being charged. The bigger the appliance, the bigger the change in the number. Over time, you learn by observation how the system works, how much energy you have, how much your appliances use, when to conserve, and when to think up ways to use the surplus.

Sizing the Battery Bank
This is quite important because either too large or too small a battery bank will result in a shortened battery life or much more charging required from a backup generator. Either way expenses go up.
   There are many very complicated methods of calculating the battery bank size, but I find them to be inaccurate and unnecessary. These methods would have you try to figure out the use of every electrical light and appliance and then decide how much it will take to power this very approximate, theoretical load for some number of days with zero sun. Well, real life varies so much that it makes sense to approach this question differently.
   Here’s my method. Assume that a one person household requires 5 kWh per day for everything including lights, all appliances, and media devices. A two person household requires 8.5 kWh per day. A three person household requires 11  kWh per day and you can add 3 kWh for each person after that. You can see that the first few people need the most energy because there are certain uses such as refrigeration that only change marginally as people are added. A light bulb lights a room just as well for four people as it does for one. Three people watching the same TV does not change the amount of energy used. Of course, people whose lifestyle makes them large consumers of electricity at night, may need to start with kWh requirements that are 20% higher because more of the energy that they use will be stored in batteries.
   Next, use a chart to determine how many average peak hours of sunlight you have. For example, by using the charts in the Appendix at the end of this book it can be determined that where I live, in Hawaii, I have around 4 peak hours on a year-round average. I found this out by using the Hawaii solar radiation/insolation map and then converting it to peak hours using the table below the maps.
   Now, take the required  kWh and divide it by the average peak hours which in my case would be: 5  kWh/3 = 1.66kwHr. This is the size of solar panel array that I will need to keep my battery charged; 1.66 kw or 1660 watts. Only a portion of the energy that I use is actually stored in the battery for the energy needed at night or when there is less solar electrical generation than I am using. Let’s say, the fraction of the total that I store in the battery is 25%. Then if we decide we want 3 days of night-time energy use in storage, then we will need a battery bank of 3 x (.25 x 5  kWh) = 3.75  kWh of storage. (3 days of storage is a good rule of thumb. In very cloudy places more might be required.)  However, since this storage and its conversion losses can be up to 20%, let’s add a 25% safety factor which brings it to 5kwHr of required storage. Interestingly, that is the number we began with. So, in my case, with 3 peak sun hours we store the same amount as our projected daily use.
   To get that amount of storage in a battery bank whose charging regime is maximized for long life, we are going to try to stay within a State-Of-Charge range between 40% and 90% of charge capacity. That is the sweet spot of efficiency, durability, and lowest battery lifetime-cost. Of course, this is only half the rated capacity of the battery that we will be using. So in order to have our 5 kwHr of storage we are going to use a battery bank with a total rating of 10 kWh (12 volts x 800 ampHrs = 9.6 kWh is what I actually have).
   As was mentioned earlier, the rate of discharge is related to how much efficiency is yielded in withdrawing the energy. The appropriate approximation for our purposes is the 20 hour rate of discharge also known in the trade as C20. This means that we are going to put together a battery bank whose volts multiplied by its amp hours will give us 10  kWh at the C20 discharge rate for the first person and increasing in  kWh as we add people served by the PV system. For my one person household and 12 volt system that means a battery with about 833 Amp hours at the 20 hour discharge rate.
   These numbers are approximations; they can be larger or smaller depending on your style of energy use. I am fairly conservative with my energy use, but hardly fanatical. My computer is often left running and sometimes I forget to turn off lights. I have small appliances that run 24 hours a day (cordless phones, etc.). I am a daytime person, rising at daybreak and in bed by 10:00 PM. My system is sized as I have described here and it works out very well indeed.
   Why is this so straightforward? It is because I have a backup energy generator, which is required in any event because I want uninterruptible power under every conceivable circumstance. This gives a tremendous amount of flexibility. You can always add more photovoltaic panels if you find your batteries are too quickly depleted. Or you can always top up your batteries from your backup source. Most importantly, you don’t purchase more battery capacity than you need.
   My system for one person plus occasional guests is 1850 watts of panels charging a 12 volt battery bank with 800 ampHr at the 20 hour (C20) discharge rate.
12 Volt x 800 AmpHr = 9.6  kWh of battery storage, of which I generally only use 50%. This system performs well with very occasional use of the backup generator.

The Inverter
Inverters are electronic devices that change Direct Current (DC) electricity into Alternating Current (AC) electricity.
Photovoltaic panels generate DC electricity that is appropriate for storing in a battery. DC can also be used directly in some types of light fixtures and appliances, but DC equipment is not widely available and tends to be more expensive, with fewer features and a shorter life than most AC lights and appliances. Thus, we utilize an inverter to make standard household AC electricity so we can have the full range of choice in the best equipment available.
   I am not going to get too deeply into the technical details of how inverters work, except where understanding is crucial to making decisions as to which inverter is right for you.
   Inverters take a DC electrical current which flows in one direction and changes it into an oscillating AC current that flows back and forth. Strictly speaking, AC electricity does not flow through the line. It oscillates in place. However, this is sufficient movement of the electricity to get the job done.
   The rate of oscillation in the United States system is 60 cycles per second (also called 60 Hz which means the same thing). In Europe and some other places 50 cycles per second is the standard. In order to oscillate back and forth, the flow rises to a peak (positive voltage) and then falls to a trough (negative voltage) in a wave form called a sine wave. It looks like this:
   The vertical position of the central horizontal line represents zero volts. The vertical height of the wave represents voltage that oscillates in opposite directions going from positive to negative electric current. The wavelength is the duration of one of the cycles and the horizontal line represents time. This is the form of the AC electricity provided by the power company. It is also called a true or pure sine wave.
   The inverter in a photovoltaic energy system has to take the DC power and make a useful approximation of the true sine wave. There are two general approaches to doing this. The first is called a quasi- or modified sine wave. The difference between pure and modified sine waves can be seen in the diagram below.
   The modified sine wave introduces steps in the oscillating pattern by using large switching devices that turn the DC on and off and then reverse the direction of current flow within a single wavelength.
   In the diagram below, the very primitive stepped wave is yellow. Such a primitive wave form can be found in the cheapest inverters. They are very noisy, and will not run many types of AC equipment. Only a true or pure sine wave inverter will run all types of AC appliances. 
   However, there is an intermediate type of inverter called a quasi- or modified sine wave inverter which much more closely approximates a true sine wave. Its waveform looks something like the yellow diagram below. This is an electronically generated approximation of a true sine wave. The better stepped wave inverters can have as many as 400 steps per cycle.
   This is close enough to the true sine wave to run nearly all AC equipment and has an added benefit of being highly efficient in converting the DC to AC, with up to 95% overall efficiency. In this type of stepped modified sine wave inverter there is still a bit of residual noisiness that can be detected in some audio equipment and simple telephones.
   Only the true sine wave inverter can run all AC equipment and generates no noise in audio or video equipment. The most efficient of these true sine wave inverters has generally less than 90% peak efficiency. So there is a cost for that ultra-clean power. In my opinion, it is worth it. If you use 5% more energy because of your inverter, it is easy to add that much more photovoltaic generating power to make up for the difference.
   True or pure sine wave electric power also has the added benefit of being much easier on your appliances, resulting in longer lasting motors and electronic equipment. It pays for itself in the long run. In addition, because it generates less radio frequency energy, it may be the more healthful alternative.

How to Get the Most out of Any Inverter
As previously mentioned, inverter efficiency is a factor in how much of the energy that you generate actually gets through to power your equipment. There are ways to maximize this. If you use the energy during daylight hours as it is being generated, you end up with more energy.
   Why? Because when the photovoltaic panels are charging the battery they also are powering your inverter. The energy that goes to the inverter during the day does not have to come from the battery, thus avoiding the 10% or so losses in the battery system. Instead the panels are, in effect, directly powering the inverter. The result is you have more energy to use.
   Here is another advantage of daytime inverter use. The inverter is designed to use a certain standard input voltage such as 12, 24, or 48 volts, depending on system design. If a 12 volt inverter gets 14 volts from the solar panels (which is often the case because the panels are charging the batteries at a higher voltage) then the inverter adjusts by drawing less amperage.
   This means that less energy is used to power your loads during the day than at night when the voltage is lower because at night there is no PV generation to raise the voltage. If you are powering a 100 watt load at 12 volts at night it will draw 8.33 amps from the batteries. If you power it during the day when the voltage is at 14 volts, you will only draw 7.14 amps—a  reduction of 16%. It is still the same number of watts, but those are watts that would not be available under a lower nighttime voltage. Plus you are saving the 10% losses that you would incur by storing the electricity in batteries.
   That is why there is a huge gain to be had by doing your large electric-demand chores during the sunlight when the battery voltage is elevated. You are in effect storing energy in the end product such as clean clothes, chipped yard waste, or sawn lumber. These forms of storage are 100% efficient.
   All of these tasks that require substantial draw on the energy system are most advantageously accomplished during the daylight hours when the incoming DC voltage is high. In my 12 volt based system, I generally look for the voltage to be over 13.5 volts before I do my laundry.

Sizing the Inverter
An inverter’s specifications include the DC voltage input (12, 24, or 48), the AC voltage output (120 VAC, 240 VAC), continuous output in watts, and surge output for starting large loads (which can momentarily draw up to 10 times their continuous needs).
   Many appliances such as refrigerators and washers use electric motors that need a larger amount of electricity at start-up than they do once the motor has reached its full speed. This surge current depends partly on how big a load the motor is trying to move.
   Inverters are designed to provide this extra power which is called the surge capacity and is shown in the chart below with load capacity versus time. The more surge capacity an inverter has the less possibility there is of overloading it.

But don’t worry about overloading it and breaking it. Inverters are engineered to protect themselves against nearly every conceivable condition. Properly set up, inverters are very robust with the exception, perhaps, of lightning. Lightning rods and surge suppressors must be used, even if an ungrounded, floating electrical system is utilized.
The loads that the inverter must handle are rarely constant. The largest start-up loads are only present for a very short period of time. The graph shows how loads in typical inverter sizes can be operated above their continuous load rating for useful periods of time.
   The time an inverter operates at a given power output is limited by the temperature of the inverter. When more heat is generated in the inverter than it can dissipate, the inverter will automatically shut down. If the overload is turned off, the inverter can be switched back on. In 30 years  the only time my inverter has shut down was once when there was a short circuit in a light switch.
   The previous graph assumes an operating temperature of 20 degrees Centigrade and resistive loads. Reactive loads such as motors or fluorescent lights will cut down the amount of time that an inverter can operate at a given load level.
   As a practical matter, the smallest inverter that should be considered for powering all modern appliances and tools is a 2400 watt inverter. This is considered a mid-power inverter, but it is what is needed for a single to three person household. It should surge to at least 6000 watts.
   In my cottage which is built for two, plus occasional guests, I use a 12 volt DC to 120 volt AC, 2400 watt (2.4 kW) modified sine-wave inverter. I also run a true sine-wave inverter of 1100 watts that is utilized for audio and video equipment that is noise sensitive. It also runs my ionizing air purifier that will not run on the modified sine-wave inverter and my Energy Star refrigerator.  
   Inverters, like many other products, are offered in a wide range of prices and for a wide range of purposes. An inverter that is intended for household use is the most durably engineered.
   Electric equipment has a specification for what is termed “duty cycle.” Duty cycle is stated as a percentage of the time that a piece of equipment can be used without over-stressing it. A 100% duty cycle rating means it can be used continuously without harm. This is the type of inverter that is appropriate for a household system.    
   Other inverters that are made for short-term temporary use such as in cars or for camping are in many cases poorly suited for a household system, not because of their power rating but because they are not engineered to last under continuous usage. That is why they are much cheaper. A quality inverter costs between 50 and 80 cents per rated watt. A modified sine wave inverter of 2400 volts with a continuous duty cycle may cost around $1,200. A true sine wave inverter with a continuous duty cycle rating of 2400 watts may cost around $1,600.
These products are generally very reliable and should last from 7-15 years depending on the manufacturer, the quality of the system design (inverter housing and ventilation are critical to long inverter life), and the protection from environmental threats such as dirt, water, insects,critters and lightning. Obviously, the inverter costs much less if it lasts 15 years than if it lasts 7 years. This is largely controllable by correct system design. There are quite a large number of reputable inverter manufacturers. Some of the names are Xantrex/Trace, Outback, ExcelTech, and SMA/Sunny Boy.

   The latest in inverter technology is micro-inverters that have one inverter attached to each PV panel. These are only used in grid-tied systems that do not use batteries. They have compelling advantages including warranties of up to 25 years, built-in MPPT charge controllers and highly sophisticated system monitoring that can be accomplished on the internet! EnPhase is the leading manufacturer of this advanced technology.

If a solar energy system uses batteries, then it is likely to employ a type of inverter that can automatically switch to being a battery charger if AC electricity is connected to its AC input. (The switch is called an automatic transfer switch.) This turns off the portion of the inverter that changes DC into AC and instead uses the external source of AC (a standby generator or the power company line) for all of your AC requirements. At the same time, it transforms the components of the inverter into a highly efficient battery charger to put DC electricity into your batteries in a sophisticated charging program. During this charging from grid or generator, the solar continues to charge your batteries as well!!  The beauty of this is that when there is not enough electricity from the sun due to dark weather or more than usual requirements for power, you always have what you need to maintain the same standard of living and you continue to harvest the full amount of solar electricity that is available!!
   While it is true that this backup comes at the expense of added fuel or electricity costs, a properly sized system will require only modest amounts of backup energy and very low annual costs. If your backup is from your own generator, then you have virtually uninterruptible power. Imagine that, no power outages!! Of course, you do have to do minimal maintenance on your generator. Change the oil every 100 hours of use. Clean the air filter. Make sure it has fuel. 

   The back up energy source can either be turned on manually when you notice a low battery voltage or you can have it turn on automatically with a specialty controller like the one here ($300).
   In my experience, a manual switch makes more sense since conditions are always changing. When my batteries reach about 12.10 volts (rarely), I turn on my backup generator. When the batteries are at this low a state of charge, they charge up at 90% or better efficiency; definitely the optimal circumstances for utilizing backup power. The energy that powers the loads is simply passed through so there is little loss when this energy is used directly. 

   My generator has a remote on-off switch, in the kitchen, so that I can easily  turn it on without having to go outside to the generator shed. Just to make sure that I don’t forget to turn it off, there is an indicator light when it is running and a timer so I can set it and forget it. I build my own remote controllers out of automotive switches, indicator lights, and DC timers. These are also available as complete kits with panels and wiring from Recreational Vehicle equipment manufacturers.
   The same sort of arrangement can be made for a connection that supplies backup power from the grid, except that these are set up with AC switches, lights, and timers. Newer programmable inverters like the Outback FX series have this function included with the inverter programmer option called the Mate  Whenever I use my backup power, I also try to operate as many energy intensive chores as possible, since the most efficient way to use my backup generator is to use at least 50% of its capacity. So, I do the laundry, I use my electric chipper shredder for making mulch, I use my table saw… any activity that will not later need to be drawn out of my batteries. This dramatically increases the energy availability of your overall system. Although in most cases I find that running my generator for 15-30 minutes is all that is required.

The Back-up Battery Charger
Generator requirements for many inverter-chargers are based on the fact that the maximum charge rate of the charger is dependent on the peak voltage available from the generator. Because the battery charger only uses the top portion of the sine wave, small variations in the peak voltage can mean a large variation in the amount of energy that goes to the charger.
   Public AC power has a peak voltage of 164 volts in a 120 VAC circuit. To maintain this voltage with an AC generator requires a powerful generator to deliver the current necessary to operate the charger at its maximum charging rate. Smaller generators have the top of their waveform clipped and provide substantially reduced power for battery charging. It will not harm anything to run the charger at these reduced rates, but it limits the battery charging rate which means it takes longer to charge the batteries.
   Therefore, if possible, choose a generator with a peak AC voltage of 164 VAC or in the case of 230 VAC circuits, look for a peak AC voltage of 330 VAC. Determine this with a normal non-RMS AC voltmeter.

How to Choose the Right Backup Power Source

Choosing how to supply your backup power is both a cost and convenience issue. I purchased a gasoline powered 6500 watt electric-start Honda generator and paid $2,600 for it. I also paid about that much to build a concrete block enclosure to house the generator and make it very quiet. That is the highest expenditure in my system. (At the low price of PV panels these days ( ), you might consider spending that money on panels that only get switched on in the darkest weather) 

The reason I made this investment is that I am not already connected to the power company. Their power grid is not close-by and therefore, hooking up would be at least as costly as the generator option and probably much more. The major advantage to the generator is that it is more reliable than the power company. Power company outages often occur under the same conditions as those where you find yourself needing more power than the sun can  provide. Storms with high winds and dark gray clouds are typically when the power company outages occur. In my area at least ten outages a year can be anticipated, although many of them are short. My generator only fails if it is out of fuel or oil, and I can easily remedy that. So, all-in-all, for an uninterruptible power supply a generator backup is the way to go.
I expect my generator to last (without any need for service other than an occasional oil change) for at least 20 years because it gets very light-duty use. $5,200 / (20 x 12 months) = ~$22 per month for equipment cost and approximately 25 gallons of fuel annually = $8.33 a month (@4$/gal.).
So I pay $22 + $8.33 = $30.33/month for generator costs. That is quite a lot on a continuing basis, but I always have uninterruptible power. If you make the decision to connect to the power company, you will pay a minimum charge to be connected and then you will be charged for whatever energy you actually use when you have the need for backup power. 
   My guess is that after the one-time costs of connecting are paid, then the grid can supply you with backup power at a bit less than  the cost of owning your own generator. The reduced reliability of the power company is somewhat offset by the reduced costs, reduced maintenance, and the convenience of never having to get fuel. If you are already hooked to the grid, then this makes the decision a bit easier. You can start out with grid backup and if you find that reliability becomes an issue you can always buy a stand-alone generator.
   Of course, you may decide to forego the uninterruptible power supply and purchase $5,200 more PV panels that only come on on dark cloudy days. This is definitely the way to go if you use the grid for backup. That will provide you with a solar-only energy system that is about 99.99% reliable. However, without generator or the grid for backup that 99.99.% reliability in this case means a day or two per year with insufficient energy. Ultimately, it is your call depending on what you can live with and the system that best suits your needs.

Housing a Generator
If you decide to go the generator route, then there is an additional cost that I previously mentioned. That is the cost of building an enclosure for your generator. In order to last for a long time generators should be well-protected from the weather, insects, dust, and other hazards. They should also be enclosed so that the sound, when running, is not an annoyance to you or your neighbors.
I generally build an enclosure of hollow concrete blocks on a concrete slab. I fill the hollow blocks with sand to dampen sound transmission. I make the roof with 2x4 wood framing that is filled with sound insulation and covered with plywood on top and concrete board on the bottom. On top, I use an inexpensive roofing material called roll roofing. It is like a heavy tar-paper with large grains of sand attached to it. It lasts for decades, comes in a variety of colors, and is dirt cheap. My sheds are built slightly off-level so that the flat roof will drain in a direction away from the door.
   The generator shed does not require standing room. The only time you need to access it is to change oil or do minor maintenance. The generator can be oriented in the shed so that the oil changing can be accomplished while kneeling in front of the door. By minimizing the size of the shed, the costs are minimized.
   An enclosed generator shed requires a push-fan to force air through the shed for cooling. As long as you utilize a fan of sufficient air-moving capacity, the size of the shed can be small. I generally have a 5 foot by 5 foot floor and a 4 foot high ceiling.
I select a location for the shed that is within 50 feet of the house but is downwind, so that any fumes from the generator will not blow toward the house.

Generators emit carbon monoxide which is poisonous—a single generator can produce a hundred times more of the colorless, odorless gas than a modern car's exhaust. Research from the National Institute of Standards and Technology (NIST) shows that users, to be safe, may need to keep generators as much as 25 feet from the house. Carbon monoxide can enter a house through a number of airflow paths, such as doors or windows.
   If possible, I sink the enclosure into the ground on the side of a slope which deadens the sound even more than a free-standing above-ground structure. In this case, a barrier of gravel should be placed against the buried wall so that water can drain and not leak into the shed.
   Passing through my tilted shed roof is a serpentine vent that is sound baffled. An electric fan forces cooling air into a baffled opening in the door of the shed. The fan is connected to the generator AC output so that it automatically comes on with the generator. This, coupled with the natural rising of heated air out the top, provides adequate airflow. The generator has both an over-temperature and a low oil pressure shut-off switch built into it. It shuts down automatically if the temperature inside the shed is too hot or the oil is low. 

I utilize a stainless steel, dial thermometer of the kind used in boiler systems and mount it so as to make it visible from outside the shed. As a result, it is always easy to monitor the temperature inside. Unexplained rises in temperature would be early warning for mechanical and efficiency problems. This saves a lot of expense in repairs that come only after catastrophic failure. Make sure this thermometer goes up to at least the boiling point of water. Your generator shed will probably run at a continuous 130 to 165 degrees Fahrenheit depending on the size of the fan/blower.
The fuel tank for the generator is placed outside of this room in a protected enclosure that is easily available for fuelling. An electric automotive fuel pump and timer are attached to a hose that can pump fuel directly from the tank of my car to the generator’s fuel tank. This way, I never have to touch the fuel. The process is easily accomplished even for a non-technical person who might also have difficulty handling a five gallon gasoline jug.

I have found it useful to utilize a used automotive gas tank because it can also use a conveniently mounted remote gas gauge. This can be easily connected to and powered by the generator’s starter battery which is 12 volts just like a car. A panel can be mounted above the gas tank for the gas gauge and the fuel pump switch/timer. By experiment, I found that my fuel pump could pump five gallons in ten minutes. Knowing that I had a 15 gallon tank, it made it simple to set the timer to a certain amount and do other things while the gas was being transferred. Alternatively there are more expensive gas transfer pumps available that pump so quickly that little time is used in transferring gas to your generator. These cost $400+.
I have run a system like the one described here that had zero problems for 16 years. I did replace the generator after 16 years. But I had many fewer solar panels in those days and used my generator much more.Such a system is very quiet, durable, and low cost.

Financing Solar
The first step required to understanding the financing part of solar is to be able to estimate what kind of costs you will be incurring. The following is a simplified process for estimating the cost of a household photovoltaic system.

Estimating Household Solar Energy System Costs
Number of people in household
unit ($)
PV panels
Charge controller
watt- hours
Backup generator
System Assembly
/ mat.

SubTotalDo-It-Yourself Cost

Contractor Profit (20%)

SubTotal costCost w/ Contractor

The following table uses the individual’s Peak Sun Hours and multiples that number to obtain an adjusted estimated cost based upon the available sunlight. The more sunlight the better the cost savings.
Peak Sun Hours
 Sun Hour Multiplier
Number of people in household
This section compensates for the fact that solar energy varies by geographical location. See the maps and charts in the Appendix (Pg. 87) for peak sun hours in your area.

You can further refine this chart by estimating your energy-use habits. If you are careful in the way you use energy, these figures will work well. If you are an average householder, you can add 15% to these figures. If you don’t pay any attention to how you use energy, then you can double these estimated system costs. Tax incentives can reduce the costs up to 50%! (See Pg. 74)
  When you have done this rough estimating process you can contact Clean Power Finance:  or at:
Clean Power Finance, Inc.                   Phone: 866-525-2123 
222 7th Street - 2nd Floor                    Fax: (415) 520-5668                                             San Francisco, CA 94103-4004           Email:
   They can fill you in on financing for your solar system. Of course, home equity and other forms of low-cost, low-interest loans are worth investigating. Clearly, the less you pay for financing the faster and greater your return on investment. With energy prices skyrocketing, solar energy is your best choice in the medium-to-long term.
For grid-tied systems, Go Solar for $0 Down.
Now you can afford to go solar without the high initial cost of installing a system. Instead of buying the equipment, you simply lease it. Solar Lease is the most popular residential solar financing option in the country! Visit this site for more information:

Solar Energy Tax Incentives
U.S. Tax incentives can be found here:
They vary widely from state to state. The federal government also offers generous incentives. These incentives, if properly planned for, can reduce the cost of your system by 50% or more. Often, installers are well versed in the strategies for maximizing these benefits. Generally, all of the costs of the system are eligible including panels, panel mounting structures, trackers, inverters, charge controllers, wiring, disconnect and breaker boxes, switches, instrumentation, remote controls, heat exchangers, pumps, batteries and many other items.
   In my opinion, taking into account the complete package of benefits of solar, these tax incentives are icing on the cake. After all, what is it worth to have energy security without threat to the natural systems—air, water, and land.  I figure that is worth a lot more than the price of a used car per person served. But there is also a social good in speeding up the process of conversion to clean energy that is light on the earth. So, all in all, these tax incentives serve an important function.
State by State Tax Incentives, Rebates, and Subsidies can be found here:

Updated Information
Updates to information in this book as well as valuable links and references can be found at the companion web site

The Appendix of Technical Information is only available in the printed book .

Photo Credits

Chixoy: Roof mounted panels, (Pg. 43)

David Monniaux: Ground mounted solar water heater, (Pg. 22) Ground mounted solar panels, (Pg. 41)

Department of Energy, Tracking solar panels, (Pg. 41)

Morningstar Corporation, Charge controller,

(Pg. 48)

NOAA: Solar Barn, (Pg. 42)

OutBack Power Systems Inc., Charge Controller, (Pg. 48)

Sun Frost, Refrigerator, (Pg. 15)

Surette/Rolls Battery Company Limited, Batteries, (Pg. 45, 52), Hydro Caps (Pg. 52)

Takagi Industrial Co. USA, Water heater, (Pg. 20)

Utah Geological Survey, Inverter, (Pg. 63)

 About The Author
Author: Jonathan Cole
Jonathan Cole is a solar energy pioneer and international authority and consultant on solar energy systems and design. Having lived with solar energy systems of his own design for 28 years, he is uniquely qualified to advise those who want to join the solar revolution. Jonathan has a Master Degree in Business and has set himself the mission of accelerating the transition to solar energy. Jonathan also has a Web log about solar at:

Jonathan can be contacted at:
Andrew Walsh- Editor
Andrew Walsh has spent years living in remote communities with no centralized power, giving him a thorough insight to the practicalities of living off the grid. Having relied upon solar, wind, and biodiesel to fuel his energy consumption, he understands that designing and maintaining renewable energy systems is practical and necessary. Utilizing his background as a writer, graphic designer, and conservation biologist, he continues to look for new ways to integrate renewable science and systems into the public mindset.