Solar panels promise to lower your electricity bill by supplementing the energy you buy from the local power company. But choosing and installing solar panels can be an overwhelming task.

Solar cells, which are linked together in a panel, convert sunlight into electricity via photovoltaic materials, such as silicon. When sunlight hits these materials, the light's energy is absorbed, and that energy causes electrons within the material to escape from their position in the atom of silicon or other photovoltaic material. These released electrons are captured to produce an electric current.

As of the third quarter of 2014, more than 17,500 megawatts of cumulative solar electric capacity are operating in the United States, which is enough to power more than 3.5 million average American homes, according to the Solar Energy Industries Association. Residential solar panels were the fastest-growing category, with 58 percent growth during the quarter, the association reports.