Southern California Edison said Thursday that it plans to install $875 million worth of rooftop solar panels in order to meet peak demand and new state environmental requirements.

The Rosemead-based utility sought regulatory approval to place photovoltaic panels on 2 square miles of commercial roofs over the next five years, the company said in a statement.

The project would generate 250 megawatts of electricity, or about enough for 162,000 homes.

Edison said that because of the sheer volume of the project and recent technical advances, the cost of the panels will be half that of other solar-power installations in the state.

Edison hopes to have some of the panels fully operational by August, in an effort to help the company meet state laws requiring reduction of greenhouse-gas emissions to 1990 levels by 2020 as well as to help with summer demand.

Edison also announced earlier this month that it has also begun work on the biggest U.S. transmission project for wind energy. The project is scheduled to be finished by 2013 and will be capable of carrying 4,500 megawatts of electricity, much of it from turbines in the windy Tehachapi area of northern Los Angeles County and eastern Kern County. The lines will bring power from the wind farm to about 3 million California homes, Edison said.