Just 15 percent to 20 percent of new single-family homes built include solar, according to Bob Raymer, technical director for the California Building Industry Association. The proposed new rules would deviate slightly from another much-heralded objective: Requiring all new homes be "net-zero," meaning they would produce enough solar power to offset all electricity and natural gas consumed over the course of a year. New thinking has made that goal obsolete, state officials say. True "zero-net-energy" homes still rely on the electric power grid at night, they explained, a time when more generating plants come online using fossil fuels to generate power. In addition to widespread adoption of solar power, the new provisions include a push to increase battery storage and increase reliance on electricity over natural gas.