After all of the bolts have been installed holding the rails to the “L” brackets, the panels are bolted to the rails (see Photo 3)

.

Photo 3. L bracket and rail joint.

Photo 4 shows the same as photo 1 except that the string locations are delineated on the photo. Because of the roof geometry on my house, it was not possible to put three strings of panels with all of the panels orientated in the same direction.

Photo 4. Panels with the 3 strings identified.

Consequently, the first and second rows of panels are orientated with the long axis perpendicular to the eaves with the third row orientated parallel to the eves, with the remainder of the third string of panels adjacent to the second string. This filled up the entire southern exposure of my roof, and works out very well.

The junction box that you see at the left end of string 1, brings all of the wires from the three strings into a common box and then takes these wires down through the roof to the inverter below. Actually, there are 7 wires. The positive and negative wires from each of the three strings and the ground wire that is attached to every panel and every rail. These wires enter a common housing and go through the roof using a weather -proof fixture. These seven wires go down to the inverter and are wired into it, along with surge protectors to guard against damage in the event of a lightning strike.

The inverter is shown in photo 5.

Photo 5. Inverter. Wires to left come from the solar panels. Switch to right is for solar vent fan.

The wires coming from the roof (the solar panels) pass down to the left of the inverter and enter at the bottom. The wires coming out of the inverter, contained in the flexible metal conduit go directly to the fuse box for the house. They are wired into a 40 amp breaker in the fuse box and this is where the AC power goes into the house and also into the electrical grid through the electric meter.

In terms of complexity, this is a very simple system. It consists of PV panels, wiring, inverter, and wiring. The inverter is awesome in that it decides when to active itself, it decides when to shut itself off, it decides what the characteristics of the AC system coming into your house are, and then matches the AC current generated by itself exactly to those characteristics. If the line voltage coming into your home varies, the inverter varies the voltage coming from the PV system to exactly match it, and if the line voltage coming into your home is interrupted, the inverter shuts itself off and waits until the line voltage is again what it should be before it turns itself back on. My only question is “Why must the best unit on the market be German made and not made in the USA?”

The only other part of the system is the NET METER. That is discussed under that appropriate question. By the way, I was able to operate my system in a test mode prior to having the net meter installed. My electric meter would spin backwards when I was producing more electricity than I was using---That is a really cool feeling. However, I have heard of one other PV operator who’s electric meter would not operate in reverse. I have no explanation for that.

ANSWERS TO POSED QUESTIONS:

Q-1. SHOULD I INSTALL A SOLAR HOT WATER HEATER?

The answer to this is an emphatic YES!!!! The reasoning behind this answer is as follows: Your energy consumption in your home is composed approximately 30% of energy to heat water. If you have a $200.00 per month water bill, and you heat your water with an electric water heater, you are paying about $60.00 per month for water heating. If your electric rate is 12 cents per kilowatt-hour, then you are using 500 Kw-hrs per month to heat your water. If you were to put in a solar water heater, it would cost you about $4500.00 installed and its operating cost in Florida is zero. The pump that circulates the water to the 4 foot by 10 foot panel on your roof is powered by a small PV panel (12” by 12”), and consequently requires no power from the electrical system to operate the solar water heater.

Photo 6. Solar hot water heater panel on roof. Note PV panel to run the circulation pump on this end.

Photo 7. Solar hot water heater tank. Note pump on left piping stack. The gray line going to the left

And into the wall is the back up electrical. We have not ever had to use it.

If you were to install a PV system to heat the water, you would need one that would produce 500 Kw-hr/30 days per month = 16.6 Kw-hr per day. A rule of thumb for Florida is that you get 5 hours per day at the rated capacity. Therefore, you would need 16.6 Kw-hr/5 hr = 3.3 kilowatts. PV systems cost between $7.00 and $9.00/ watt, installed. Therefore, using $8.00/watt, it would cost you 3,300 x $8.00 = $26,400.00 to install the PV system to heat your water. This compares to the above figure of $4,500.00. By installing a solar water heater, you save $21,900.00. That is why my answer is so emphatic.

By the way, if you are using gas to heat your water, you would possibly save less than $60.00 per month. Gas is supposed to be cheaper. That was not my experience. We had a gas water heat, had it removed and installed an electric heater. Our overall utility bill went down by an estimated $40.00 per month. However, we were renting our gas water heater and because we were gone several months per year, out minimum charges skewed our bill.

Q-2. HOW BIG SHOULD MY SYSTEM BE?

Q-3. HOW MANY DOLLARS AM I WILLING TO SPEND TO REDUCE OR ELIMINATE MY ELECTRIC BILL.

I have combined these two questions, because they are related. You size your system to totally eliminate your electric bill, and then you look at your bank account and decide how much you can afford. Because the quote you will get from your PV installer is based on approximately $8.00 per installed watt of capacity, you can just prorate the size of the PV system in accordance with your available funds.

For example, if you decide that it takes a 10 kw system to eliminate your electric bill, this will cost about $80,000.00. If you only have $40,00.00 available, you will be able to reduce your electric bill by half.

Keep in mind that Florida Light and Power, the State of Florida, and the local regulatory agency considers that the maximum size domestic system that you can install is 10 kw. If your system is larger than that, it becomes classified as a commercial system and everything becomes much more difficult. I do not know all that is involved in a commercial installation, but it is my understanding that it can cost as much as 20% more to install. On the other hand, if you do decide to install a commercial power plant (yes--that is what it would be), the incentive program cap on the rebate goes from $20,000.00 to $100,000.00. All information in this paper relates to a domestic system.

Lets get to the sizing of your system. Grab up all of your last year’s electric bills. It doesn’t matter what month you start with, but you must end with the previous month. Your electric bill has the number of kilowatt hours that you used for every month listed. Copy these down, add them up and then divide by 12. This will give you the number of kw-hrs, on the average, that you use each month. Now, if you heated your water with electricity for that year, and IF you are going to install solar water heating, multiply that average monthly usage by 0.7. I will use an example so you can easily follow along. Assume that your annual usage is 24,000 kw-hrs per year. This is probably an average usage for a family of 3 to 5 persons in Brevard county. Divide that by 12 months 24,000/12 = 2,000 kw-hrs per month. Take 0.7of that

2,000 x 0.7 = 1400 kw-hr per month.

For estimating, we will use 30 days per month which yields 1400/30 = 46.6 kw-hr per day. As in the calculations from question 1, we will use 5 hours per day at rated production. This means that we divide the 46.6 by 5 or 46.6 kw-hr per day/ 5 hours per day = 9.32 kw. This means that in order to eliminate this family’s electric bill, they would have to install a PV system that has a nominal capacity of 9,320 watts. At $8.00 per watt, the cost of this system would be 9,320 x $8.00 = $74,560.00. Because the system size is less that 10 Kw, it complies with a residential system.

The amount that this system actually costs will depend of several factors. If the contractor is not busy, he will probably bid less per watt than if he is full up for the next 3 months. Because this system is fairly large, it will require 2 inverters, which cost roughly $7,000.00 each, so the system may be more expensive than one that could get by with a single inverter. For example, my system has a 7 KW inverter, the largest that this company makes. Therefore, I got a slightly better quote. The reason for my smaller system is that our family is very conservative with our energy usage and a 7Kw system covers all of our electric needs except water heating, which we do with a newly installed solar water heater.

For the example family using 2,000 kw-hrs per month, they will need to spend $75,000.00 for the PV system and an additional $4,500.00 for the solar water heater. They will then be classified as a zero energy home. If they cannot afford that much expenditure, they will have to down size their PV system.

Q-4. SHOULD I GO OFF THE GRID OR RIDE THE GRID?

Definitions are in order. What does it mean to go off the grid? It means that you disconnect from the electric utility entirely. This means that you generate power when the sun is shinning and you must store it for when the sun is not shinning. Energy storage usually means batteries. I do not recommend this type of PV system unless you are going to radically alter your energy consumption life style. Going off the grid will not be discussed in this paper.

Alternatively, you can ride the grid. This means putting energy into the utility lines when the sun is shinning and you are producing more than you need and then taking electricity out of the grid when the sun is not shinning. This is the system that I use and the one that suits 95% of the American public. You do not have to buy and operate an energy storage system. Your neighbors use the excess energy during the sunny portion of the day, which also happens to be the time of day during the highest demand in Florida because of our use of air conditioning. This means that your electric meter must run forward and backwards and this will be discussed in questions 22,23, and 25 under the net metering program.

Q-5. WHAT EFFICIENCY PANEL SHOULD I USE?

You will read in the news papers about PV cells that have efficiencies of 40% or higher. These are still in the laboratories and have not reached production yet, so do not think about them. By the way, the panel efficiency is a measure of the amount of energy that falls on the panel in the form of sunlight with respect to the amount of energy that ends up in the electrical wires coming from the panel to your inverter.

I considered three panel manufacturers for my PV system. Their panels had efficiencies of 12%, 12.5% and 14%. The 12% and 12.5% cost about the same, but the 14% panels cost $1.00 per watt more. We had room on our roof for the lower efficiency panels, so we used them. All of the panels had the same performance warranty (question 14), so we purchased the lower efficiency panels.

Basically this question boils down to your available roof area. If you have lots of roof area, than you can use the lower efficiency panels. If not, you will have to go with the higher efficiency and more costly panels.

Q-6. WHERE SHOULD I PUT MY PANELS?

This seems like a silly question at first, but it is not. Some people have a small lot, so it is necessary to put the panels on the roof. Other people have a large lot so they can consider placing the panels on the ground. Some house roofs are shaded by trees, which the owner does not want to cut down, so the panels must go elsewhere. Some people have a work shop roof that is large enough to placed the panels on. You must decide where to put your panels.

To help you make that decision, you will get about 12 watts per square foot of panel. The range seems to be from 10 to 15 watts per square foot. The higher number equates to higher efficiency and higher price. My system was 12 watts per square foot. I wanted 7,000 watts, so I needed 7,000/12 = 583 square feet. Our example family above wanted 9,320 watts so they need to have 9,320/10 = 932 square feet for the lowest efficiency or 9,320/15 = 621 square feet for the very highest efficiency panels.

By the way, panels come in all sizes but for our purposes, you will use panels that have wattage ratings from 175 watts per panel to 210 watts per panel. I have not seen panels with higher ratings that this. All of these panels are roughly 3 feet by 5 feet.

Q-7 WHERE SHOULD I PUT MY INVERTER?

The inverter can be placed either in-doors or out-of-doors. I have seen both installations. You must check with the manufacturer of your particular inverter whether it is placed inside or outside. If it is not weather-proof, it must be placed inside or a special enclosure must be constructed around it. Personally, I would never place it outside. First off, it is expensive and an easy target for vandals or thieves. Secondly, it is hooked up to 240 VAC with a 40 amp breaker. That is enough electricity to kill some one several times over. In addition, if it gets rainfall on it, even if it is weather proof, there is the potential for a short. When your inverter goes down, your whole PV system is down.

When the inverter is operating, particularly between the hours of 11 AM and 4 PM, it is generating quite a lot of heat. I put mine in the laundry room next to the garage. It sits right next to the solar water heater tank. When my wife is drying clothes in the laundry room, the temperature at the top of the laundry room gets above 100 degrees F. To cut down on this heat, I installed a solar attic ventilation fan directly over the inverter. I mounted the two 15 watt solar panels on some extra mounting rails on the roof and ran the wires through the attic. This fan starts up about 8 AM on a sunny day and is really humming by 10 AM. It discharges directly into the attic above the garage, pulling air in from the leaks around the garage door. This fan is so effective that the temperature in the laundry room has dropped over 20 degrees on a hot day. The heat problem was solved but the solar fan and panels cost me $200.00.

So you see, you should mount the inverter in a place where it is protected from vandals, thieves, and the weather. It should not be mounted in your air conditioned space because the heat load will just cause you to use more electricity. It should be vented to lower the heat load and if you can incorporate an attic fan just as I did, it will cool the area around the inverter as well as dump cooling air into the attic. Using a solar attic fan makes this a wining situation all around.

Q-8. AM I CONCERNED WITH THE ARCHITECTUAL LOOK OF MY HOME?

Q-9. HOW MUCH AM I WILLING TO SPEND TO PRESERVE THAT LOOK?

If you have a home on the North side of your street, you solar panels will have to be on the side facing the street. They must face south to maximize the winter time output. For most of us, that is not important, it even may be an advantage, because your next door neighbors can keep an eye on the array. For those of you who are concerned about this look, there are lots of design steps that you can take to make the array look better. Most manufacturers will make the panels in almost any shape that you want. For example, if you have a South facing roof that intersects with another roof, the end panels of the array can be made up with the proper angle so that the array parallels that intersection.

I do not have any cost of these special panels, but my solar contractor said that you should expect to pay significantly more for this ½ panel of ¼ panel than you would for a regular panel. If it is worth it to you, go for it. Incidentally, it you have an architectural review board in your sub-division, you should run this by them for approval prior to contracting for the installation.

Q-10. HOW MUCH OF MY ROOF WILL BE COVERED WITH PV PANELS.

To a great extent, this was covered in question 6. You will need a roof or other area of about 85 square feet per kilowatt. This should be a South facing roof. For an easy rule of thumb, take the square footage of the air conditioned portion of your home and multiply by 0.4. That will be the square footage of your roof that is available for solar panels. The 0.4 figure comes from the fact that most houses have half of their roof facing South or close to it. The other 10% accounts for dormers, intersecting roofs, etc. that usually appear on the roof of a house. This is just a course rule of thumb, and the exact dimensions of your roof will be evaluated by your solar contractor before he will give you a quote.

My home has 2000 square feet under air conditioning and we required 583 square feet of solar panel space available. This comes out awfully close to 0.3. The reason that mine is less than others is that we do not use as much electricity as the average home.

Q-11. WHAT DO I DO IF I DO NOT HAVE A ROOF WITH SOUTHERN EXPOSURE?

Be prepared to pay a little more for your PV system than someone who has southern exposure. It is critical for the winter operation of your solar panels that they be tilted towards the South. The way this is accomplished on a roof that has exposure other than to the South is for the contractor to place two or three of the corners of the panel on legs. These legs may be 2 or 3 feet long, depending on the pitch of your roof.

There are several disadvantages to this installation procedure. The first is higher initial cost. The second is looks---you are creating a terrace system on your roof---but then who really cares. The third is that it is probable that a significant portion of your array will be shaded by the roof peak in the early morning hours and late afternoon hours, so you should count on diminished output from this array as compared to one that has southern exposure. The fourth is that the wind can get hold of the panels better during a high wind---make that a hurricane ----and so the anchoring system must be better. These all contribute to a higher initial cost.

There is one major advantage. The backs of these panels are more open to the air and the heat build up on the panels, which causes temperature fade, will be markedly less. This may be enough to overcome the shading by the peak of your roof and you may actually get as good or better production in the summer time as someone who has a South facing roof. As we all know, everything we do has its plusses and minuses.

Q-12. WILL THE ROOFING ON MY HOME BE COMPATIBLE WITH THE PV PANELS?

The people who design these fastening systems are a very ingenious lot. They have a fastening system that will work for almost any roofing system. I had asphalt shingles on my roof, and that is the most common, so I did not have any problems. When the solar contractor left my house, they were going to a metal roofed house and they had special attachment brackets that attached to the ridge where the two pieces of roofing met. When you are shopping for your solar contractor, get this ironed out with them before you contract, and have it in the contract. The local regulatory agency will require that the solar contractor submit engineering drawings and data to show that the solar panels will stay on your house for the winds that are expected in your area.

The most important thing to remember here is have a nearly new roof on your house. I have heard that the cost of re-roofing your house with solar panels on it is roughly double what it would be without the panels.

Q-13. WILL IT COST ME MORE IF I LIVE ON THE BEACH?

YES. Everything costs more if you live on the beach. That is the American way of doing things. However, there is a good reason for that in this case. In most cases it is just the “soak it to those rich fools” concept. If you live on the beach, or close to it, the hold down system must be designed to withstand a 140 mph wind. This requires a “L” bracket every 2 feet on the attachment rail. If you live 10 miles West of the Indian River, the wind load is so much lower that an “L” bracket is required every 6 feet. Aluminum is expensive and the installation of three times as many “L” brackets is expensive. This is required by your local regulatory agency and it is to protect your solar panels from flying away in a hurricane. I do not know of any other requirements that will cost more on the beach other than corrosion and all of you who live on the beach are very familiar with that cost. My installer used aluminum brackets and rails and stainless steel bolts all around. You cannot do better than that.

Q-14. WHAT IS THE LENGTH OF THE WARRANTY FOR THE SYSTEM COMPONENTS?

The inverter is warranted for 10 years. The PV panels have a performance warranty. My panels are warranted to produce 85% of their rated capacity at 15 years and 80% of their rated capacity at 25 years. My contractor said that his work is guaranteed for one year. My system is still working very well after one year, so I have no experience on how reliable the warranties are.

Q-15. CAN I OPERATE THE SYSTEM IF I HAVE NO TECHNICAL EXPERIENCE?

It is difficult for me to answer this question. I am a techie. However, it is my opinion that anyone can be trained to monitor their PV system and then call your installing contractor if some of the parameters are out of their normal range. Your inverter puts out about 10 pieces of data every one or two minutes. Once you are taught to read and record these data, you are fully prepared to determine if your system is functioning properly. I would estimate that you need to read and record these data once per day or once per week to properly evaluate the system. Once you understand what the data mean, it can be exciting to see your PV system generating energy.

Q-16. IS THIS PROVEN TECHNOLOGY?

Absolutely. Some PV systems have been operating for 30 years and if tended properly are producing nearly their original rated capacity. Also the technology has improved some over that 30 years.

This technology is what I call one of the HO HUM systems. If installed properly, its operation is very HO HUM. Boring!! And of course, that is what you want.

Q-17. WHAT IS THE FINANCIAL RECOVERY PERIOD FOR THIS INVESTMENT?

I will use the data for my PV system. My 7 Kw system cost $50,000.00 installed. I will get a rebate from the State of Florida of $20,000.00. I can deduct an amount from my 2009 income taxes equal to 30% of the remainder or 30% of $30,000.00 which is $9,000.00. This means that my true installed cost is $21,000.00. My PV system will save me approximately $100.00 per month (that is equal to 833 Kw-hrs). One hundred dollars per month is equal to $1200.00 per year. Divide $1200.00 by $21,000.00 and my rate of return is 5.7%. All other things being equal, the pay back time is 17.5 years. But, of course, all other things are not equal. I have laid out the dollars for the installation, and if it continues to work well, my costs will not increase, but the price of electric service will surely go up. If I produce more electricity than my family uses, at the end of a year FPL will pay me the retail rate for this energy. That will increase the rate of return.

I have not included the replacement of the inverter. It is warranted for only 10 years, so it is not intelligent to expect it to last much beyond that time. My inverter currently costs $9,000.00. So a cost of approximately $12,000.00 should be entered at the 10 year time (of course the price will go up). I have not done the analysis of this expected cost. It will obviously decrease the return rate and increase the pay back period. However, from my perspective the reduction of my family’s carbon footprint, I would install the system at 50% higher cost. Refer to question 27 for a discussion of the alteration of our carbon footprint.

Q-18. HOW WILL MY PV SYSTEM FAIR IN A HURRICANE.

My system is designed to withstand 140 mph winds. I will be quite surprised if it really does stay intact with that high of a wind. I would expect the rails to remain fixed to the roof as long as the roof stays attached to the house. However, because of the way the panels are attached to the rails, I would expect that to be the failure point. One of the things that we did in my installation was to keep the panels some distance from the eaves and peak of the roof. This provides a wind break for the panels and should reduce the lifting force of the wind. In addition to that, we installed the panels with a 10 inch gap between string 1 and string 2 (refer back to photo 2). This was for maintenance and washing of the panels. About 1 month ago, I moved the lower row (string 1) up to abut the panels of string 2. I did this to provide a chimney effect for cooling, but it also removes a gap where the wind can get hold of the panels. It will either make it better or worse---I hope that I never am able to evaluate this change---let those hurricanes go some where else.

You might ask why I am not more worried about this. Well, I have enough to worry about without being concerned about something that I can do nothing about. If the regulatory agency believes that the panels will stay on the roof in a 140 mph wind---at least they have given it some consideration.

Q-19. WHAT WILL HAPPEN IF I GET A LIGHTENING STRIKE ON MY PV SYSTEM?

I asked the same question of my installer and they assured me that all of the panels and all of the rails are grounded so the lightening should go to ground and probably not harm the equipment (see Photo 6).

Photo 8. Notice grounding cable from right to left..

They also did something else that I did not know about. They installed a surge protector on both the DC system and the AC system. When the lightening strike comes, the surge protectors will tend to protect the inverter. If it is a direct strike, it will probably not be enough. However, these are normal and proper electrical procedures. There is one procedure that I do not like and will alter. The ground wire was dutifully attached to every panel and every rail and then it was run down to the inverter where it goes into my electrical panel and then to ground. I will check with my electrician, but I would feel a lot better about this system if a wire was run over the edge of the roof, down to the ground and then connected to a 6 foot long stake in the ground. This would encourage the electrical strike to go directly to ground and not to my inverter. At a minimum it would dilute the amperage going to my inverter. If I had my way, the ground would not even go through my inverter. I will work this problem and let you know what I find out.

The only other consideration is what happens if I get a lightening strike. Am I covered with my homeowner’s policy. I should check, but I have not as of yet.

Q-20. WILL MY HOUSE INSURANCE GO UP IF I INSTALL A PV SYSTEM?

Here I can only relate my experience. Before we contracted for the system, I called our insurer, Liberty Mutual. They told me that they would cover the system, not to do anything until it was installed and then call them. I did that. We are currently covered for the solar water heater and the PV system with our usual deductibles. We changed some things on our coverage, ending up with basically the same coverage as before with a slightly higher deductible. The increase in our premium was less than $50.00 per year. However, if we had not adjusted some things, it is my recollection that our premium would have gone up about $250.00 per year. Our insurance company had no problem with the addition and they just consider it an integral part of our house. Please call your insurance company and inquire what they would do.

Q-21. WILL MY PROPERTY TAXES GO UP IF I INSTALL A PV SYSTEM?

The Florida legislature passed a bill one or two years ago that forbids the local taxing authority from increasing the value of your home if you install energy saving devices. Wellllll, you draw your own conclusion on that one. Classify me as a doubting Larry. The last time they raised our taxes on our home in an abnormal fashion, they said that they finally discovered after 35 years that we had a garage.

Q-22. WHAT IS THE “NET METERING PROGRAM” WITH THE UTILITY COMPANY?

Get on the internet and look up the net metering program for your utility. For FPL, it basically says that you must sign a net metering contract with them. They will install a net meter within 30 days of the contract signing. This meter will keep track of how much electricity you use from their utility and how much you contribute to their utility. At end of a year the account will be settled up and you start over. There will be a monthly book keeping charge. You will pay retail for the electricity and they will pay you retail for the electricity.

As of this writing, we have not had our first month on the net metering program, so I can not tell you what happens every month. I will modify this when I know.

Q-23. HOW DO I GET THE NET METERING PROGRAM STARTED?

On the day that our contractor started the installation of our system, he walked into our house and handed us the complete application for the net metering program. He had filled out his portion and told us how to complete our portion. He then told us to mail it by certified mail. The form was in the mail before the job was completed. IF your contractor does not agree to do this, get another contractor.

When the job was completed and inspected by the Brevard County building department, our contractor advised us to send a copy of the approved and inspected building permit along with a copy of the first page of our home insurance policy showing that we have at least $100,000.00 liability coverage. We did this, via certified mail and then waited. After 4 weeks, we got a letter from FPL with our signed contract saying that she needed the building permit and insurance. We faxed a copy to her, e-mailed a copy to her and then called her 5 times over the next 2 weeks. After 2 weeks, we got a call from her asking for the building permit and the insurance. My wife went ballistic, but the FPL employee called back and said that she had found it. She assured us that we would have out net meter within 10 days. After two weeks, I called and she had no idea where our papers were. She called back the next day and said she had found them and we would get the meter soon. Three days later I was reaching for the phone when the door bell rang---the FPL meter installer was there. He installed the meter and explained how it worked. We are now in the system.

Fifty eight days after we finished the installation of the system, we received our net meter. During that time, we tested our system extensively and had produced 1321 Kw-hrs of electricity. Our electric meter had advance 14 Kw-hrs in that time and we were operating only part time. Yes, we were testing the system and I have kept detailed data. I will share that with you later.

An interesting aside to this story is my conversation with the meter installer. I told him that we had been operating the system for testing purposes. My comment was that I sure would have liked to seen the meter reader’s face when he read the meter and it was about the same as for the previous month. The meter installer chuckled and informed me that he would have liked to seen my face when I realized that the reader had retagged our meter with a yellow tag. I asked what the yellow tag meant and he said that it meant that I had been stealing electricity. Out bill for April showed a usage of 12 Kw-hrs with a total bill of just over $7.00.

Q-24. HOW DOES THE NET METERING METER WORK?

This will not be explained to you by FPL unless you get the man who installed our meter and you happen to be home. The net meter is an electronic meter and will show you three windows. Each window stays up for about 10 seconds and then goes to the next. This continues. The first window is a bunch of eights.

Ignore this. It tells the meter reader if the meter is working OK. The second window has a big plus sign on the left side and numbers after that.

This is the amount of kw-hrs that FPL has supplied to you since the meter was installed. The third window has a large negative on the left and numbers after that.

This is the amount of kw-hrs you have supplied to FPL. For all of these windows, there are dashes under the numbers. If the dashers are moving from left to right then you are using power from FPL. If these dashes are moving from right to left, you are providing power to FPL. If they are standing still, you are using all of the electricity that you are generating.

Q-25. HOW DO I KEEP TRACK OF THE AMOUNT OF ELECTRICITY THAT I HAVE PRODUCED?

The net meter will not tell you how much electricity you have produced, only how much has passed through the meter each way. Your inverter will come with a data window, so make sure to mount the inverter so that you can easily read this window. My inverter has 5 windows that each come up and stay for 5 seconds and then advance to the next window. These windows show the following:

Window 1. Shows the voltage on each of the two legs of your AC system. My inverter usually

Shows 119 volts on the left leg and 121 volts on the right leg. You may

Ignore this data.

Window 2. Shows pounds of carbon dioxide saved. This is just a multiplicative factor on the

Kw-hrs produced. It is interesting to note.

Window 3. Shows pack voltage and current production rate in watts. Pack voltage for my system

Runs between 340 volts and 285 volts depending on the production rate.

My wattage runs between zero and slightly over 7000 watts. I have seen an

Energy production rate in excess of 7,000 watts only 4 or 5 times.

Window 4. Shows Kw-hrs produced today and something else--get this worked out.

Window 5. Shows total Kw-hrs produced since the inverter started up and the total time the

System has operated.

If you are going to keep a log so that you or someone else can evaluate how your system is performing, then it is NOT necessary to record all of these windows. Only the data in window 3 and window 5. Window 3 will tell you the most about the health of your system, but it is important that this data be recorded at the same time every day or week and that this time be in the time zone of maximum production for your system (between 11 AM and 3PM). For example you might log data every day when you go out to lunch or you might log data every Sunday when you come home from church. Log at least once per week. Once per month will not give you enough data to properly evaluate your system. By the way, I log 16 pieces of data between 5 and 15 times per day. After 3 months of this, I have enough data to know that the data and data frequency that I am recommending is adequate. Your data sheet should have column headers as follows:

Date Time Weather Volts-pack Watts Kw-hrs Hours Other (your net meter data )

Make up a blank data sheet and make several copies. Clip these on a clip board and hang it next to your inverter. When one data sheet is full, put it into a file---these data are more valuable if the analyzing agent can look at trends. If you are out of town a lot, or if you are not anal enough to do this, give your lawn guy a couple of extra bucks a week and have him do it.

Q-26. HOW DO I APPLY FOR MY REBATE FROM THE STATE OF FLORIDA?

In a fashion similar to the FPL application, my solar installer walked into the house and handed me an application for the rebate with his portion filled out. We mailed it off to the State of Florida via certified mail and are currently on their list awaiting payment, when it is funded.   We received our check for the rebate on January 26, 2010 (about 9 months after we applied).  Once again, if your contractor does not agree to do this, get another contractor.

Q-27. HOW WILL MY CARBON FOOTPRINT CHANGE AFTER THE INSTALLATION OF MY

PV SYSTEM?

This is the question that gets me on my soap box. I have been an environmental engineer for 35 years. It is my belief that we all should ask the question---who should do something about the unfathomable amount of carbon dioxide that we are putting into the atmosphere? We should then immediately hold a mirror in front of our face and say “HE or SHE SHOULD”.

The next question is---will it make a difference? You cannot truly understand how much of a difference it will make until you do the calculations. Lets do that now.

In Florida, we produce most of our electricity from carbonaceous materials (coal, petroleum and natural gas). That most is 81% from carbonaceous materials. Only 19% is from other sources, principally nuclear. The SUNSHINE STATE produces less than one half of one percent of our electricity from solar.

According to a 2005 Department of Energy survey, and from published figures for the amount of carbon dioxide produced by each of these carbonaceous energy sources, we produce 1.505 pounds of carbon dioxide per kilowatt-hour that we produce, at the generating station. Adding a 13% line loss and all other losses, we get a figure of 1.7 pounds of carbon dioxide produced per Kw-hr of electricity delivered to our home. This just happens to be the multiplicative factor that my inverter uses when it calculates the pounds of carbon dioxide saved.

Referring back to our average family in question 2 and 3, we see that this family uses 24,000 Kw-hrs of electricity per year. If we assume that this family installs the solar hot water heater and the 9.3 kilowatts PV capacity, they will buy zero kw-hrs from the utility in the next year. If we multiply their energy usage by the 1.7 pounds of carbon dioxide per kw-hr, we get 24,000 x 1.7 = 40,800 pounds of carbon dioxide that they will not be putting into the atmosphere because of installation of the solar systems. This is a whopping 24.4 TONS of carbon dioxide that will not go into the atmosphere this year, and next year, and the next year, etc. All of this from just one family making a commitment to changing the world.

FORGET about the economics and the pay back----just be mighty proud that you can reduce your carbon foot print by this much. My family’s carbon foot print reduction is about 13 tons per year. I want to make a bumper sticker about 12 feet high that says “I REDUCED MY CARBON FOOTPRINT BY 13 TONS PER YEAR---WHAT HAVE YOU DONE FOR YOUR WORLD”. But of course, I won’t. Instead I will write papers like this and give talks to community groups like yourself and hope to make an even bigger difference.

WHAT IS MY CARBON FOOT PRINT? As I had people review this document, it became apparent that a lot of people do not know what the term “carbon foot print” means. I will explain and give some examples. Picture your self walking through a bed of sand. You leave foot prints behind. Picture your self eating a candy bar and discarding the wrapper. Picture your self drinking a soda and discarding the can. When you look back, you see your trash in your foot prints. This is your trash foot print. In a similar fashion, whenever we burn anything that has carbon in it, we leave behind carbon dioxide.

Unfortunately, you cannot see this carbon dioxide, but it is still there and contributing to global warming. For simplicity, the carbon dioxide foot print has been shortened to your carbon foot print. When you breath, you expel carbon dioxide. When you drive an automobile, you burn gasoline and expel carbon dioxide. When you turn on a light, you use electricity, which was probably generated using a carbon fuel such as coal or gas or petroleum and the power plant expels carbon dioxide.

In an attempt to illustrate just how much carbon dioxide we contribute to the environment, I have compiled the amount of carbon dioxide what a typical couple of two contributes each year. These data are in Table 1.

          Table 1. Carbon Dioxide Contributed by a Couple Per Year

          ----------------------------------------------------------------------------

          ITEM                           AMOUNT CONVERSION                                      POUNDS PER YEAR

          ---------------------------------------------------------------------------------------------------------------------

          Electricity                    24,000 Kw-hr 1.7 #/Kw-hr(in Florida)                           40,800

          Auto                           40,000 miles 20#/gallon, 20mpg                                  40,000

          Breathing                    calculated from respiration rates for 2 people                  9,000

          Air Travel                   50,000 miles 100 hrs,500gph,20#/gal,150passengers      13,300

          Secondary*                 see explanation below                                                 16,000

          ------------------------------------------------------------------------------------------------------------------------

          Total                                                                                                         104,700

                    *Secondary includes food growing, processing and delivery, as well as entertainment

                                   And is influenced by your life style. See www.CarbonFootprint.com

The first thing to notice is how big the amount is: 104,700 pounds or 52.35 tons of carbon dioxide. The second thing is to notice how much of that total is contributed by transportation (53,300 lbs for auto and air, which is 51% of the total). And the third thing to notice is the amount contributed by electricity (40,800 lbs which is 40% of the total). Photo voltaic panels can reduce this to zero.

I told you I would get on my soap box !!!

Q-28. HOW LONG WILL IT TAKE TO INSTALL MY PV SYSTEM?

I can only relate how long it took my contractor. Two men arrived on the first day. They laid out the system, installed 1/3 of the rails and 12 of the panels. The second day these same two men returned and finished all of the rails. The other panels had not arrived yet. The electricians came mid morning and worked to mid afternoon hanging the inverter and re-arranging some electrical in our laundry room. The third day the two roof guys brought the rest of the panels, installed them, installed the ground wiring and hooked up the wiring from panel to panel and secured all of the wires in place. The electricians hooked all seven wires in the junction box, ran the wires down to the inverter, hooked the inverter to the AC panel and at about 2 PM we powered the system up. It worked right away.

Q-29. WHAT HAPPENS IF MY ROOF LEAKS AFTER THE INSTALLATION?

A good contractor will specify that they are responsible for any roof leaks caused by their work. That same responsible contractor will give you a one year warranty for the same. The only caveat that I have here is if your roof is not in good condition before the installation, you should not install the panels over this roof. Most contractors will recognize this and either not contract or exclude any leak warranty.

Q-30. WHAT SHOULD THE CONTRACT WITH THE SOLAR CONTRACTOR LOOK LIKE?

Every contractor has their own contract that they will provide you with. When you are interviewing contractors, ask them for a copy of their contract. After interviewing 3 or 4 contractors, compare the contracts. Select the best points of all of them and then combine them. Then take these salient points to your attorney and have him write a contract that favors you.

That is my advice. I DID NOT TAKE MY OWN ADVICE !!! I signed the contract that my contractor presented, with all of the write over and crossed-off phrases. However, I protected myself by specifying that I would not make the prepayment of ½ of the contract amount until I had 12 of the panels and the inverter in my garage. That was entirely acceptable to the contractor and it gave me some financial assurance because the retail price of that equipment was almost equal to the amount of the deposit that I had given him.

Q-31. HOW DO I PROTECT MYSELF AFTER THE CONTRACTOR HAS DONE THE WORK?

This is perhaps the most important part of the contract, because you do not want to pay for the materials or labor twice. If the contractor decides not to pay either his subcontractors or his suppliers and instead take that money and go to the Bahamas, you are in trouble. His subcontractors or suppliers will come to you and demand payment. If you refuse, they can file a lien on your property and you will have to pay this lien before you can get clear title if you should decide to sell your home. Your contract should specify that the solar contractor provide you with a list of all of his subcontractors and suppliers at the beginning of the project. This list should include names, addresses, telephone numbers.

It should be specified in the contract that the final payment, usually 10%, will not be paid until you have release of liens from ALL of those on the list. I think that these release of liens are supposed to be filed in the court house, but you will have to check with you attorney about that. For me, just having them in hand and signed originals is good enough, but if you suspect something, carry your cell phone with you and place a call to any that represent large sums and /or may be out of state. Most contractors get their panels and inverters from a single supplier and this is the one you should be most worried about. If you contractor will not agree to do this, run out of his office and do not come back no matter what the price of the quote.

Q-32. HOW DO I DETERMINE THE BEST CONTRACTOR TO DO THE JOB?

This questions trumps all of the other questions about contracts and contractors. ONLY USE A LOCAL CONTRACTOR. The local contractor is familiar with your local regulatory agencies. He or she knows which one is the correct one to contact for the construction permit. The local contractor will have worked with these individuals at the regulatory agency before and know their do’s and don’t’s. The major reason to use a local contractor is that they make their living in your community and know that the only thing that they have going for them is their reputation. If they skimp on a contract or do a bad job, word will get around in the community and they will have a harder time getting work.

So, when you look for contractors, look only at local contractors, ask them for a list of previous clients that they worked for, check that list carefully asking these contacts for other names of clients because the contractor will only give you names of satisfied customers, and then visit at least 3 of the contractors previous installations. If the contractor doesn’t have three completed projects, then you should quietly excuse yourself and leave. Keep in mind that not every one of a contractors previous clients is going to be entirely satisfied--we have all seen that individual who cannot have a single thing done by an outside contractor with out ending up in court.

Visiting job sites with your prospective contractor will get you more familiar with how the systems should look installed. You should be looking for neatness, attention to detail and listening to the contractor as to how many excuses he presents for a job not well done. Conscientious contractors do not fill their presentations with reasons why the job was not done right---they point out the good points and generally express a pride in workmanship.

Selecting the right contractor makes all of the rest of the job a breeze. You might take a cue from our experience. After we had basically selected the contractor we wanted to do the job, we contracted with him to install our solar water heater. This is a small job compared to the larger PV system ($4500 compared to $50,000). Our contractor sent two men to do the job. The arrive at 8:15AM and had completed the job and were gone by 11:30 AM. I spent the entire morning watching them and checking on their work. My background includes stints at carpentry, plumbing, electrical as well as multifamily maintenance, so I have a lot of hands-on experience. The installation job was equal or superior to anything that I would have done. They were definitely going to be my contractor for the PV job. By the way, the short time that they spent on the job told me that they had done the work before and knew exactly what to bring to the job site. They did not have to spend half the day going to the various supply shops to get materials. There is about 10 pieces of specialized materials that are used only on solar water heater installations that they not only had with them, but had them installed before I could even ask what they were.

Q-33. DO I DARE GO ON VACTION WITH MY PV SYSTEM OPERATING?

I am writing this paper while on a two or three month trip. My son is checking on the system a couple of times per week and logging data for me. The only operational mode you have is to turn the system on or turn it off. There are no other controls. The major advantage of having it operational when you are gone is that you are not there using electricity. After two weeks of operation on the net meter, we were 50 Kw-hrs behind. After two weeks of operation when we were not there, we were 150 Kw-hrs ahead. I will update these numbers later.

Q-34. CAN I INSTALL MY OWN SYSTEM?

IF you are a licensed contractor, or a licensed electrician approved for solar installation then you can install your own system. If you try to install you own system without being licensed, you will not be able to get a building permit. Without the permit, you cannot get into the net metering program. You must have a licensed contractor install the system or you will not be eligible for the rebate program. If you are going off the grid and do not care about the rebate program, I think you would be able to get your building permit--but you should ask your regulatory agency first.

Q-35. SHOULD I CONTRACT WITH A SUPPLIER WHO SPECIFIES THAT YOU GET YOUR

OWN INSTALLER?

The basic problem with this scenario is that if anything goes wrong, you have two suppliers pointing their fingers at each other. In effect you would become the primary contractor and the other two parties would be your subcontractors. You would be asking the installer to take responsibility for permit application and probably liability for the job. I think that you would have a hard time getting a qualified contractor to agree to this without his fee being very high. Keep in mind that the contractor gets a much cheaper price on the equipment than you would be able to get and he figures that into the job when he is preparing your quote.

Who is going to fill out the forms? Who is going to resolve the issue if the inverter is not compatible with the panels? Well, you see some of the problems. You might be interested to know that I priced my PV system costs on the internet. The retail price of my panels and inverter was only $4,000.00 less than the contract for my entire system installed. I did not add the cost of the hold down system and the wiring or any of the labor.

Q-36. SHOULD I GO WITH A COMPANY WHO HAS “NEW” TECHNOLOGY?

Simply put----not unless you are willing to correct the technology if it doesn’t work or throw the whole shebang away and start over.

Q-37. WHAT IS THE ADVANTAGE OF HAVING A SINGLE INVERTER RATHER THAN HAVING

AN INVERTER ON EACH PANEL?

We were approached by a company out of Orlando that has a system with an inverter on every panel. They claimed that it was superior to a single inverter, but I could not find any justification for that claim. I thought about it for a long time and have never been able to rationalize in my mind whether it is better or worse. This was the same company that wanted me to contract with my own installer and their price was not low enough for me to even consider their proposal. If someone has any technical reasons for the advantage or disadvantage of the muplti-inverter system, please let me know.

PERFORMANCE OF MY PV SYSTEM.

At the time of this writing, I have been operating my PV system for one year. I cannot operate this type of system without looking at it in detail. Part of my looking at it in detail is to install additional monitoring equipment. I installed a voltage gauge and an amp meter on each of my three strings. This allows me to keep track of each of the strings, and also to see if one of the strings is producing less or more power than the other two strings. See photo 7 for an up close view of these gauges.

Photo 9. Voltage and Amp gauges to monitor each string. Operating at 1 PM.

Consequently, I will have more data available than you would if you installed the same inverter that I have (A Sunny Boy).

So far, all three strings are producing identical voltages and amperes. There are so much alike, that I am logging data only from string 1. I have selected a typical sunny day, May 10, 2009 and will present my data from that day in graphical form. Keep in mind that I log data only when I can remember to, or whenever I am walking through the utility room. Generally, this is every hour, but if I get busy on some other project, there will be a gap in the logged data. All of the data points are observed data. There has been no smoothing of the data or estimating. The time of the day is displayed in military time, because my computer program would not plot it otherwise. Remember 1 PM is 13, 2PM is 14, 3 PM is 15, 4 PM is 16, 5 PM is 17 and 6 PM is 18.

Figure 1 is a plot of the variation of the pack voltage with respect to the time of the day. At 5 AM when is still dark, the pack voltage is zero and the inverter is still shut down for the night. At 6 AM the voltage has risen to 250 volts and the inverter wakes up. That is an appropriate term because you can hear it clicking and dinging. It will not start operation until the voltage reaches 250 VDC and even then there is virtually no energy production. Remember, at 6 AM the sun is not over the horizon. Sunrise on the 10^th of May was about 7:15. By 8 AM, the voltage was at 325 volts. It had probably been higher, but I missed that data. The open voltage for this pack is 432 volts. Open voltage means the voltage of the pack if there is no current flow and the positive and negative wires for the pack are not connected, and the sun is shining full on the panels. From 8 o’clock on the voltage falls until it bottoms out around 12:30 PM. It stays at this lower value until about 2:30 PM and then it starts back up again. It peaks at about 7 PM and then as the daylight diminishes, the voltage also diminishes and at dark goes back to zero.

The data in figure 2. Is derived from the amp meter on string 1. The current flow starts out at zero and by 6:50 is 0.1 amps, increases until about noon with a peak of 7.0 amps. The current flow stays at that level until 2:30 PM and then decreases until it goes to zero at about 8 PM.

The data in figure 3. Is the electrical energy production rate, in watts, taken from the information window of the inverter. It has the same shape as the current flow graph. If you take the current flow maximum (7.0 amps)from figure 2 and multiply it by the voltage minimum (300 VDC) from figure 1., you get 2,100 watts. Why doesn’t this match the value from figure 3?? Remember that the three strings are in parallel, so you have to add their current. Three times 7 is 21 and 21 times 300 is 6,300 watts. That is almost exactly what the peak for figure 3 equals.

Figure 4 shows the accumulation of energy, in Kw-hrs, for the 10^th of May. This data was also derived from one of the windows of the inverter. These data form a modified “S” curve. The energy production starts slowly, picks up in the middle of the day and then slows down at the end of the day. Total energy production for that day was 48.5 Kw-hrs. That is way above the design production of this system. It is supposed to produce 7 Kw for 5 hours which would be 35 Kw-hrs. Keep in mind that I have selected a nearly ideal day for PV production. It is in the Spring, which is cool, the days are getting longer, and the angle of the sun is nearly ideal with respect to the angle of my roof.

The contrast between the energy production of a nearly ideal day and a very lousy day is presented in Figure 5. May 17, 2009 was another nearly ideal day. Energy production on that day was 50.3 Kw-hrs. Contrast that with May 23, 2009 which was a day in which the sun did not directly contact the ground. It was cloudy and rained several times during the day. The energy production for that day was only 21.4 Kw-hrs. That is less than half the production for the 17^th, but is still 61% of the design production. Not bad for a lousy day.

I have lots of other data, most of it concerned with temperature fade. However, what I found is that even on the hottest days, the energy production level was still above 40 Kw-hrs per day. If the day was sunny, the temperature fade provided a maximum energy rate of up to 1000 watts less, but because the days were much longer, the total production for the day was still above the design level. I will look closer at this data for July and August and see if the trend still holds.

It is interesting to watch the change in the energy production rate when a cloud obscures the sun over the panel. In the middle of the day, the pack will be producing 6000 watts, a cloud shadow comes over, and the production rate drops to 1000 watts in less than a minute. When the cloud shadow clears, the production rate goes right back up.

If there are high ice crystal clouds that precede a front, the energy production will be down 10 to 20% for the day. I also observed one day that there was a light fluffy cloud layer that came over near noon. It appeared more like fog than a cloud. While that cloud was over the house, I was getting production rates of over 7,000 watts for about 20 minutes. When it cleared, my production rate went back down to less than 6,800 watts. I have an explanation for this phenomena, but it is beyond the purview of this paper.

I have kept track of the electrical production since start up, but on a long term basis, I have kept track of the energy production since our net meter was installed on June 2, 2009.

That production is shown in Figure 6. There seems to be a little wavering about a straight line in the first several days of production, but a straight line fit’s the data very nicely. Given that it is a straight line, the slope represents the average daily production. That slope is 41.85 Kw-hr per day. This is somewhat greater than the 35 Kw-hr per day that the system was designed to produce.

The production rate fell off rather sharply in the winter months. I went back to all of my data and plotted the production rate for each month. The slope of that plot represented the daily production rate, on the average. Figure 7 shows these production rates.

The production rate started out at approximately 43 Kw-hrs per day for the month of June and then basically dropped for each month thereafter until December. The 18 Kw-hr rate for December reflects the shorter days as well as the fact that we had a lot of cloudy weather in December of 2009. After December, the production rate went back up, reflecting the longer daylight periods. In April and May, the rate was back up to 42 Kw-hrs per day.

The return of the production rate to the 42 to 43 Kw-hrs per day indicates that the system is still operating very close to the same as the day it was installed. There is no apparent deterioration of the photo voltaic cells.

If you add up all of the monthly averaged production rates shown in Figure 7 and then divide by 12 you get 34.33 Kw-hrs per day as the annually averaged daily production rate. This is very close to the 35 Kw-hrs that the system was designed to produce (we got this by multiplying the maximum rated production rate, 7 Kw times 5 hours per day). If you take the total electricity production rate for the year (13,800 minus 1200) and divide by 365 days per year you get a daily production rate of 34.52 Kw-hrs per day. Once again, very close to the 35 Kw-hrs per day that we assumed during the design phase.

The positive and negative readings from the net meter are shown in Figure 8, along with the difference

between these two readings (termed the NET POWER). Remember, that the positive readings are the Kw-hrs that we owe to FPL and the negative readings are the Kw-hrs that FPL owes to us. Initially, FPL was the winner, and as the warm weather came upon us about the 10^th day, the gap widened. Because we were watching the usage very closely, we started to notice on about the 10^th day that our air conditioner was running almost non-stop during the day. On the 12^th day, we called our AC repair man and he found that our AC system had leaked out some of it’s refrigerant. He recharged it, and our operating time for the AC diminished markedly. This is illustrated on the 13^th day when the amount of power on the negative readings rose significantly. By the 15^th day, they were close to being the same amount and then we left for vacation. Our son continued the readings, and it is obvious that we reduced the amount of electricity that we were using.

If we subtract the positive readings from the negative readings, the relationship between the amount of electricity we were producing and the amount we were using becomes even more dramatic. Below the line readings indicate that we owe FPL and readings above the line indicate that FPL owes us.

The interesting thing to note here is that if we had not been watching our electrical consumption so closely, we probably would not have caught the problem with the air conditioner. At least, we would not have caught it so soon.

Earlier in this presentation, I told you that we were supposed to buy our power at retail and sell our power at retail. It seems that FPL has a different way of figuring retail than I do. Right after the first of the year, we got a credit on our electric bill of $5X.XX. We assumed that our account had been credited incorrectly. When we chased it down, we found that the credit was for 1,668 Kw-hrs purchased by FPL from us. When I calculated the rate, it came out to 3.8 cents per kilowatt hour. We pay 12 cents per kilowatt hour, including all of the miscellaneous charges.

I called the net metering program for FPL and they told me that they keep track of the cost of the power that they purchase and that came out to 3.8 cents per kilowatt hour for 2009. To me, that it the wholesale cost of electricity, but the person I spoke with seemed to think that was exactly what I should be paid for the electricity. Somewhere along the way, I have been given some bad information--I guess. What made this doubly irritating was that we had the coldest winter in 20 years and we heat our house with electricity. This meant that in December we sold 1668 Kw-hrs of energy to FPL for 3.8 cents and then in January we had to buy back 500 Kw-hrs of energy at 12 cents.

We have been paying $6.04 per month for reading the meter. That cost, along with the purchase of our electricity by FPL, plus another rebate meant that our electricity for the 12 months beginning June 2009 was approximately $42.00. NOT BAD.

One of the interesting phenomena that occurs after you install energy producing or energy savings devices is that you become very aware of your energy usage. Everyone goes through this. In our case, we have installed a new high efficiency air conditioner. In addition, we have installed all new energy efficient windows and patio doors. This means that we are using less energy than we have in the past. This is apparent when you look at our net power usage in Figure 8. The slope of the NET POWER curve between the 15^th and the 80^th day is almost the same as the slope between the 300^th and 360^th day. This means that our net energy usage for the early summer of 2010 is the same as our net energy usage when we had the house closed up and we were on vacation.

As you can see, I am excited about this technology. I am getting some really dirty looks of envy from friends and relatives when I tell them about out electric bills. That also gives me a high. So far, the system has met all of my expectations, but the time frame is still young. It is my hope that this dissertation will help you make the decision to invest in your own PV system and what you read here will make that process easier. The best of luck in reducing both your electric bill and your carbon foot print.