The California governor, Arnold Schwarzenegger, will take part when Southern California Edison announces the plan on Thursday. The solar panels, covering more than two square miles of rooftop, will be able to produce 250 megawatts of electricity when the sun is shining, enough to power about 160,000 homes.
Solar photovoltaic installations are usually measured in thousandths of a megawatt, and Edison’s order is roughly equal to all the solar cells produced in the United States last year.
The plan illustrates the shifting finances and growing scale of the solar industry. Once consisting mainly of small projects paid for by the owners of homes or businesses, solar installations are increasingly being financed by companies that offer cheaper electricity or lease payments in exchange for the use of a roof.
Southern California Edison faces strong growth in electricity demand, John E. Bryson, the chairman and chief executive, said in a telephone interview.
Edison is under orders from the state to produce 20 percent of its power from renewable sources by 2010, a goal Mr. Bryson said it was unlikely to meet. Among the challenges is building new transmission lines from areas that are appropriate for windmills or other renewable sources.
In contrast, the solar installations are simple, he said. “We kick this off, and we believe we will even have some on rooftops available to help meet the August summer peak,” he said. Finishing the $875 million project will take about five years, and it requires approval from state regulators.
Mr. Schwarzenegger is scheduled to appear at the announcement Thursday on the roof of a warehouse in an industrial neighborhood near the airport in Ontario, Calif.
He said in a statement, “These are the kinds of big ideas we need to meet California’s long-term energy and climate change goals.” He added that more partnerships between commercial building owners and utilities could “set off a huge wave of renewable energy growth.”
Edison plans to cut costs by putting in relatively large installations, with teams moving from building to building. Advocates hope that the project’s scale will change the basic economics of solar cells, whose power is far more expensive than conventional electricity. Southern California Edison will own the cells and install them on leased space.
The largest solar installation in this country is 14 megawatts, at Nellis Air Force Base in Nevada. The largest in the world, in Spain, is 23 megawatts. Of the top 10 worldwide, all are in Spain or Germany, except for Nellis.
While the installation is huge in solar terms, it is only about half the
size of a modest coal-fired power plant, and its energy output over a year
will be only about a fourth to a third of what a coal plant of the same size
would produce. That is because the solar plant will work only in daylight,
and produce maximum power only when the sun is directly overhead and
unobstructed by clouds.