State utility regulators have approved the $294 million sale of Southern California Edison’s share of a coal-fired power plant in New Mexico to Arizona Public Service Co.

SCE, a unit of Rosemead-based Edison International, owns a 48 percent share of two generating units at the Four Corners Generating Station.

Facing a regulatory deadline under California’s greenhouse gas emission reduction law to sell all of its coal-fired generating assets by 2016, the utility reached an agreement in November 2010 to sell its share to Arizona’s largest electric utility, subject to regulatory approvals.

The sale was approved by the California Public Utility Commission on Thursday. Commission President Michael Peevey said that once this sale is complete later this year, none of the state’s three regulated electric utilities will own any coal-fired power generating assets.

The Los Angeles Department of Water & Power still has substantial stakes in coal-fired power plants in other Western states, including the Navajo Generating Station in Arizona. L.A. Mayor Antonio Villaraigosa has announced plans for the municipal utility to be entirely coal-free by 2020.