California state regulators unanimously approved a measure yesterday that will allow Golden State residents to save up to 20 percent on their electric bills by conserving power. Beginning in July, households that use 15 to 20 percent less electricity than they used in 2000 (before the energy crisis) will receive an additional, proportional deduction from their electricity bill, under the state’s “20/20″ rebate program. The program is expensive, but regulators hope it will prevent rolling blackouts, which disrupt service and ultimately cost the state far more money. After the state’s massive energy crisis, regulators approved a more expansive version of the program that included business customers and doled out about $290 million in 20/20 rebates. Noting that the energy crisis is not over, Gov. Gray Davis (D) urged regulators to revive the program this year. Advocates say it encourages consumers to conserve energy, but some California municipalities prefer to support longer-term conservation measures, such as investing in efficient appliances.