Green Building - Solar Photovoltaics

   Solar photovoltaics, or solar panels, have come a long way.  Unsightly panels on the tops of roofs and fields are still around, but there are companies out there that have products that blend into the roof shingles.  Some even have the metal roof look.  There are several websites out there on the subject and I will list a few, but essentially, the home owner would install a system that converts the suns rays into DC power, or battery power, and stores it for later use.  The battery power must then be inverted from DC power to AC power to run lights and appliances within the home.  Again, with most newer technologies, this one is not cheap.  The only way to make the solar system work is with credits from federal and state government programs, so again, check with your local tax expert.  The class that I attended several weeks ago covered a system that is very expensive.  On average, the cost was $30 per square foot and each foot gathered about 5 watts per hour.  So for a 600 square foot 3kW hour system, the cost is around $18,000.  And this example does not take you off the grid, but rather it supplements your monthly usage.  The positive side to this is if you have an electrical provider that will buy it back from you, you could sell your power during the day when your home is in a low-usage state.  Most solar photovoltaic (SPV) companies advertise a 15-30% savings.  I will use my own power bill as an example.  I used the Texas Solar Power Company's website to roughly calculate my monthly savings.

   My average power bill runs about $200 per month.  I pay about 9.5 cents per kW hour.  That means my average electrical consumption is about 2100kW hours per month.  A kW hour is 1000 watts per hour.  A 100w light bulb uses 1/10 kW hour if left on for one hour.  So it would take the same bulb 10 hours to use one kW hour of power.  If I installed 600 square feet of SPV on my roof, it would cost me $18,000 for the initial cost of this system.  And the panels would have to face South in order to get the full benefit.  The Texas Solar Power Company says that on average, I can collect about 5.4 hours of sunlight per day (providing it is not overcast).  I collect 5 watts per square foot per hour.  So in one hour, I can store about 3kW hour of energy.  On an average day, I will have stored 16kw hours.  If I store it to use at a later time, I will need an inverter to convert from DC to AC.  The Texas Solar Power Company (TSPC) says that there is a loss of about 23% at the inverter.  When I tap into that 16kW hour, it now becomes 12.5kW hour once it has been inverted to AC power.  On average, I use about 70kW hours a day (2100kw hours divided by 30 days).  So now, I will only be using 58kW hours per day, or a savings of 17% on my power bill.  That is a savings of about $35 per month or $416 per year.  Now if I qualified for the government credits and only paid $7200 for the system vs. the $18,000, it would still take me over 17 years to break even.  The TSPC states that with a rebate program, their panels will pay for themselves in 4-9 years.  The product I used as an example looks like shingles and metal roofs vs. actual panels, which cost more than the traditional products.  In any case, it will be an investment up front, and with patience, will pay for itself over time.  It should be considered with the way that energy costs continue to rise.

   A less expensive approach would be to consider a solar water heater.  Up to 25% of your power bill may be used to heat the water in your home.  A solar water heater is less expensive and would take less time to pay back the initial investment.  The TSPC website has a checklist of what a home owner should do before investing in a SPV system.  you can do a lot to your home with a limited amount of money to save on energy costs.  Examples are investing in Energy-Star appliances, adding insulation to your home, and having an expert close-seal your crawl space and/or attic for a tighter building envelope.

Advanced Energy

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