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by Bruce Karney

A few months ago I wrote an article about 10 things that people living in the Bay Area should know before purchasing a solar photovoltaic (PV) system. That article was so popular that many follow-on questions streamed in. This article provides answers to some of those more detailed questions. If you haven't already read it, please review the original article first - it covers the basics - and then come back to finish this one.

There is a lot of excitement about new solar panel technology, but more likely than not you will choose to install modules that use the same basic technology that was available in 1984. They are a proven, long-lasting way to convert sunlight into electricity. The latest models have decent efficiency, turning about 20% of the energy that strikes them into power. New technologies continually make the news, but for the most part are only applicable to very large commercial installations, not residential rooftops.

Here are 10 more things you should know before investing in a solar system (see the original article for 1-10):

11. Some solar system critics have said that the energy produced by solar panels is less than the energy it takes to make them, and this is simply false. The energy required to manufacture your solar panels and inverter and transport them to your home is equal to about 1 to 3 years worth of the energy produced by the PV system.



12. You can buy a solar system with no money down. If your credit is sound, you can take out a home improvement loan for the entire cost of the system. If your monthly electricity bill is more than $150, the amount you spend paying back the loan plus your small residual electric bill will be less than you're paying now for electricity. In other words, your PV system will put money in your pocket every month from the first day you install it. Once the loan is paid off in 15 years or so, the amount of positive cash flow will jump dramatically.



13. Going solar will not trigger a property-tax reassessment of your home. By law, reassessments can only be triggered by improvements that expand the size of your home.



14. Once your panels are on your roof, you should tell your homeowner's insurance agent so that they can be added to your policy. This will increase your property insurance (probably by less than $10 per month), but it's very important to make sure that your solar investment is protected from damage by fire and all the other perils that your homeowner's policy covers.



15. Two kinds of solar system warranties are typically offered. The first comes from the firms that manufacture the panels and the inverters. Manufacturers' warranties are typically 20-25 years on the panels and 7-10 years on the inverters. The installation company will probably also warranty the quality of their work. For example, the installer will warranty that your system will operate properly and that there will be no leaks in your roof for a period of time, typically 3-10 years. However, neither the manufacturer's or installer's warranties cover fire or theft, which is why you need to add them to your homeowner's policy.



16. Solar panels will not damage your roof. In fact, they protect the area directly beneath them from light and heat. Our panels are on the west side of our home, above the family room where we spend most of our time in the evenings. The shade provided by 200 square feet of solar panels keeps that room much cooler during summer evenings than it used to be, even though the ceiling is pretty well insulated.



17. Speaking of roofs, it will cost more to mount solar PV panels on a Spanish tile or shake roof than on a plain old composition asphalt shingle roof. Tile and shakes are more brittle than shingles and more care must be taken to insure that the attachment points that penetrate the roof are properly sealed. This takes more time and will add 10-25% to the cost of the job.



18. Before we leave the subject of roofs, the pitch (or slope) of the roof has a strong impact on the production you can expect from your solar system, and may also affect the cost of installing it. Pitch interacts with orientation (e.g., south-facing or west-facing) in a complex way that can be modeled by your sales representative using a solar calculator. Generally speaking, a pitch of 18-22 degrees is ideal. If your roof is flat, panels can be mounted flat or "racked up" at the ideal angle to generate more power. However, racking costs more up-front, so careful analysis is needed to decide whether to install racking or not. If your roof is particularly steep the crew working on it will need to use safety harnesses. Using harnesses slows them down somewhat and adds to the cost of the job.



19. The only routine maintenance a solar system requires is hosing the dust off the panels in the summer. If you park your car in the driveway, you know how dusty it can get. Your solar panels get dusty too, and the dustier they are, the less power they produce. This effect is most noticeable if your panels are mounted flat or at a low angle. It's less of an issue if your roof is steep. We live in a one-story home and our panels are quite easy to hose down, so I do it once a month in summer. If I lived in a two-story home and the panels were harder to reach I would probably do it once or twice a season or skip it altogether. However, if I lived in a dusty area and never hosed off my panels I might lose as much as 10% of my production near the end of summer because of dust accumulation. One good rainstorm is all it takes to restore them to full production.



20. Because solar systems have no moving parts, you may wonder how you can tell if your system is working. Once it is installed, you will be able to see that in two ways. The first is the display on your inverter, the device that changes the direct current from your solar panels into the alternating (AC) current used in your home. The display on the inverter will tell you the instantaneous power output (e.g., 3,215 watts) and also the amount of energy produced so far that day (e.g., 14.218 kilowatt hours). The inverter can also tell you the total lifetime energy production from your system. So, if you make it a habit to check the lifetime figure on the first of each month, you can calculate the production for the month by subtracting the previous month's lifetime total from the current lifetime reading (e.g., July production = August 1st lifetime reading - July 1st lifetime reading). You will also get a new digital electric meter from PG&E when you go solar. It will tell you how much electricity is flowing out to the grid (meaning you're producing more than you're using) or in from the grid at any moment in time. The digital meter also keeps track of your "on-peak" and "off-peak" net production or consumption of electricity. For example, during May of this year we had net production of 174 net kilowatt hours during peak hours and net consumption of 39 kilowatt hours during off-peak hours. This generated a credit for us with PG&E of $45.66 that we will be able to use in the winter when our consumption is greater than our production.

I will conclude this article with three pieces of very important advice.

• Before you buy a solar PV system, do what you can to reduce your consumption of electricity. Conservation is cheap compared to solar panels. Search the web for "conserving electricity", read the suggestions, and implement as many as you can.
• Talk to several solar companies and get written estimates before you make a decision.
• If you are leaning toward solar after sufficient research but still hesitate to make the leap, my suggestion is: Go solar. You will be glad you did!

For questions or comments about this article, please write to us at feedback@organicpicks.com

Copyright 2007 by Bruce Karney

 

 

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