Roof-mounted solar hot water systems are often designed to look like skylights, making them more pleasing in appearance to homeowners and their neighbors. The cost of solar water heating systems declined by 30 percent between 1980 and 1990. Further cost reductions will not be as dramatic, but prices will continue to decrease as demand increases and manufacturers take advantage of economies of scale. In September 2000, Governor Davis signed Senate Bill 1345 that provides funding for solar water-heating systems as well as distributed generation systems. The Solar and Distributed Generation Grant Program is being administered by the California Energy Commission.
Sunlight strikes the collector, and the sun's heat warms the water.
The heated water comes back into the home or business. The warm water from the solar system then goes into the regular hot water system. If no one turns on a hot water tap, the water is circulated back to the roof to be heated even more. During the night, the system can be set up so that water is not pumped to the roof, preventing heat loss to the cool outside air.