Jun. 19--State regulators Thursday approved a plan to generate 500 megawatts of solar power -- enough to meet the electricity needs of up to 320,000 households -- on the roofs of commercial buildings.

Southern California Edison Co. said the California Public Utilities Commission's approval sets the stage for the world's largest solar-cell rooftop installation and will help the utility comply with state mandates for renewable energy expansion and greenhouse gas reduction.

The five-year plan provides for half of the solar power to be developed by Southern California Edison. The utility will place arrays of solar panels on about 150 rooftops it will lease from building owners in high growth areas such as Riverside and San Bernardino counties, said Edison spokesman Gil Alexander.

Edison last summer got a head start by installing a 2.4 megawatt solar system on a warehouse owned by Prologis in Fontana. The utility also is constructing a solar system at a Chino warehouse and is negotiating a third installation, Alexander said. The commission last year approved the three initial projects.

Alexander said the utility plans to install 50 additional megawatts of commercial solar rooftop capacity a year.

The remaining 250 megawatts of solar capacity will be developed by independent solar companies that will lease the commercial roof space and sell the power to Edison.

Alexander said the cost of power generated by a commercial rooftop solar system is expected to be about half the cost of solar power generated on roofs of homes and small businesses because of lager setups.

PUC President Michael R. Peevey said in a statement that commercial rooftop solar power is more expensive than power from larger-scale wind and solar plants. But he said the technology still should be part of the state's renewable energy strategy because there is a higher level of certainty about when it can be brought online.

Large-scale solar and wind projects planned in remote areas often encounter opposition from environmentalists and require the construction of expensive and controversial transmission lines. By contrast, the power that rooftop solar systems produce can be fed directly into Edison's power network.

Edison a year ago asked the PUC to approve a 250-megawatt commercial rooftop solar program that the utility would develop. Alexander said the commission added the program in which nonutility power companies can participate through competitive bidding.

"By authorizing both utility-owned and private development of these projects, we hope to get the best from both types of ownership structures, promoting competition as well as fostering the rapid development of this nascent market," Commissioner John A Bohn wrote is his statement.

Reach Leslie Berkman at 951 368-9423 or at lberkman@PE.com

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