California has one of the nation’s most ambitious renewable energy mandates – 33% of its electricity must be carbon free by 2020 – yet the price of that power had long remain locked in a black box, kept confidential by state regulators.

Not any longer. Forced by a new law to publish the electricity rates of utility contracts it has approved, the California Public Utilities Commission on Friday issued a report detailing what green energy costs consumers.

Prices paid for renewable energy ranged between 5.4 cents per kilowatt-hour in 2003 to and 13.3 cents in 2011, with an average cost 11.9 cents. However, the commission said that for contacts signed in 2011 but not counted in the report, prices fell about 30% from 2009 contract prices. Many of those contracts promise to supply electricity below the cost of energy produced by natural-gas fired power plants.

(The increase in renewable energy prices from 2003 to 2011 is a result in part earlier contracts that tied the price paid for renewable energy to prevailing natural gas costs, which spiked in 2008. Green energy prices also rose as utilities – Pacific Gas & Electric, San Diego Gas & Electric and Southern California Edison -rushed to sign […]