What are home solar systems?

Home solar systems, sometimes referred to as rooftop solar systems, are small arrays of solar photovoltaic modules that can be installed on a rooftop (see Figure 1) or mounted on stand-alone panels. These systems provide electricity to help power a single home, building, or facility. Systems can be designed to provide enough electricity when the sun is shining to eliminate the need for power from an electrical utility company or even to provide more electricity than needed that can be sold back to the utility. See OWOE: How do photovoltaic cells work to generate electricity?.

Figure 2 shows the various components that make up the simplest form of home solar system. Starting at the solar array, the sun strikes the panels and the photovoltaic reaction in the panel materials produces a flow of low voltage direct current (DC) electricity. This DC current enters into an inverter that transforms it into higher voltage alternating current (AC), which is the type of electricity required to run typical appliances and machinery. The AC current enters the main electrical panel and is then distributed throughout the house or business to meet electrical needs. The system is also connected to the utility company's electric grid through a bi-directional electrical meter. During the day, the home solar system will provide some, or all, electrical needs. When additional power is needed, for example during the night or on cloudy days, additional electricity will flow from the grid through the meter in normal fashion. When the home solar system produces more electricity than needed, the excess will flow backwards through the meter and into the grid. The home or business is only charged for the "net" reading on the meter, i.e., the amount coming in less the amount going out, so-called "net metering".

For those who don't appreciate the appearance of a rack of photovoltaic solar panels, there are now a number of options for solar roof shingles (see Figure 3). Solar shingles are photovoltaic modules that have the size and general appearance of traditional roof shingles but capture sunlight and transform it into electricity. There are several varieties of solar shingles, including shingle-sized solid panels that take the place of a number of conventional shingles in a strip, semi-rigid designs containing several silicon solar cells that are sized more like conventional shingles, and newer systems using various thin film solar cell technologies that match conventional shingles both in size and flexibility. Different models have different mounting requirements. Some can be applied directly onto roofing felt intermixed with regular asphalt shingles while others may need special installation. While the cost of solar roof shingles remains higher than that of conventional solar roof panels, they are a good option if the roof is older and must be replaced at the same time.

More complex (and expensive) rooftop solar systems incorporate battery storage systems which allow the excess electricity that is generated while the sun is shining to be stored and used at night. This allows a home or business to depend even less on power from the grid. It also provides for power during an outage when grid electricity isn't available.

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