The sun has been used to generate electrical power for years to charge batteries for watches, walk lights, navigational buoys, traffic signals, radios, satellites, and the International Space Station. Vacation houses located far away from public electrical sources have also relied on solar panels. More recently we have all seen houses in town that have solar panels on their roofs, and more of our neighboring towns are installing “solar gardens.” What’s up with that?

The answer to that question is that solar power system costs are coming down, while electricity costs are going up. In Southeastern Massachusetts, we pay almost 20 cents per kilowatt-hour for NSTAR’s electricity generated primarily from fossil fuels, and we can expect higher costs in the future. The people of Massachusetts are concerned about those high electrical costs and the long-term effects of burning fossil fuels to generate power. We worry about our country’s growing dependence on foreign oil. These concerns led me to take a careful look at solar power for my house, and here is what I found:

I located a solar energy firm, experienced in a variety of residential and commercial projects, and I asked them to submit a proposal for a solar energy installation on my roof. A representative visited my home in Marion village, looked over my electrical service, climbed up onto my roof, measured it, assessed its angle relative to the incoming sunshine through the seasons, and determined the impact of shadows on panel performance. Fortunately we have a south-facing roof with a 7-in-12 pitch, and shadowing effects would only reduce the potential solar capture by 10 percent.

A week or so later I received a well-written proposal that clearly explained what work the firm would perform, whose panels and inverters they would use, how they would tie it in to my existing electrical system, and much more detail than I can relate in this short article. They would apply for all permits and state rebates, install the entire system, commission it, and do a follow-up assessment. They offered a five-year warranty on workmanship in addition to individual component warranties that are effective for much longer periods on the panels and inverters. They explained that the electricity generated by my system would simply mix with the power on the grid and that I would continue to be billed for power that I use minus the power that I generate.

But how well and how long would the system perform, and how much would it cost? The panels and inverters should operate for at least 25 years with minimal maintenance and very minor reductions in efficiency. After state rebates, a $1,000 state tax credit, and a 30 percent federal tax credit, the cost for my system was reduced by 35-45 percent from $25,000 to $9,162. Our installer estimated that the system would generate 4050 kilowatt-hours per year, reducing our electric NSTAR bills by 65 percent. But there are additional savings we did not expect. Large savings also come from the system’s production of Solar Renewable Energy Certificates (Srecs). The details are a little complicated, but the end result is that we earn an additional $300 to $600 for every 1000 kilowatt-hours our system generates, thereby shortening the pay-back period for the whole system to between 2.8 and 4.5 years. Right now Srecs are worth about $500 per 1000 kilowatt-hours (2½ times more than the rate we pay for our NSTAR power). We will receive more than $2,000 per year in Srecs alone.

I must admit that the favorable economics of a solar energy installation like ours depends in part on generous incentives provided by the state and federal government, but I believe that the government is right to encourage us to move away from fossil fuel use. It is satisfying to know that our solar energy system helps to reduce the country’s dependence on foreign oil, slows down global warming, and cuts our personal electrical costs.

Once you get started with this home-grown electric power, you can’t help but wonder how your system is doing. Our system’s performance is clearly shown in a clever web presentation I can read from any computer connected to the internet. The presentation allows me to watch the production of each panel on our roof anywhere, anytime.

If you invest in a solar energy system like ours, you tend to watch its performance often, and you develop an interest in conserving energy in other ways. Compact fluorescent and LED light bulbs make the power you generate go much farther, you remember to turn off unused lights, and you really celebrate the sunshine!

By Bill Saltonstall