California regulators on Thursday approved a 173-mile transmission line project to bring wind and other renewable electricity to Southern California residents.

The California Public Utilities Commission said yes to the segments 4 to 11 of the Tehachapi Renewable Transmission Project proposed by the Southern California Edison. The project is set to ferry power primarily from Kern County's Tehachapi Valley to residents in San Bernardino and Los Angeles counties.

SCE said it already has started building the first three segments of the project. The three segments run 77 miles, and most of them have been completed, said Paul Klein, a spokesman for SCE.

The overall project, which will include new and upgraded transmission lines and substations, will run 250 miles when completed, and it will be able to transport 4,500 megawatts of power, enough to provide electricity to nearly 3 million homes, SCE said. It will cost roughly $1.96 billion, Klein said.

Building new or updating transmission lines is viewed as critical to support a rapid expansion of renewable energy generation in California and elsewhere in the country. Twenty-nine states and the District of Columbia are requiring their utilities to increase the amount of renewable electricity they serve to customers.

The nation's electric grid overall is old, and replacing and expanding it will be expensive (see California 'Green Transmission Lines Could Cost $15.7B and Texas Approves $5B Worth of Transmission Line Projects and Wind Growth Could Cost Eastern U.S. $80B in Transmission Lines).

SCE already has signed contracts to buy about 1,800 megawatts of wind power in the Tehachapi area, the CPUC said.

Investor-owned utilities in California are required to procure 20 percent of their electricity from renewable sources by 2010.

Although SCE cleared a key regulatory hurdle, the utility still needs approval from the U.S. Forest Service and other agencies before construction can begin for segments 4 to 11 of the Tehachapi project.

SCE said it expects to begin construction of the segments 4 to 11 in 2010, and complete it in 2014.

On Thursday, the CPUC also approved two wind power purchase agreements signed by SCE. The first, 20-year agreement will entitle SCE to buy power from a wind farm operated by Echanis, which is owned by Columbia Energy Partners, that would have up to 104 megawatts of generation capacity. It's set to be built in Oregon and brought online by mid November 2010.

The second, two-year purchase agreement is for power from Puget Sound Energy's Klondike III project. Klondike, with 50 megawatts of generation capacity, also is located in Oregon and is already operating.