One of San Onofre's two generating units, Unit 2, went into commercial operation in 1983 and provided roughly 1,100 megawatts of power to the Southern California grid. Unit 3 began operation in 1984 and had a similar generating capacity. Unit 1, a smaller unit, went into service Jan. 1, 1968, and was retired in 1992.
San Onofre was the only large Southern California power plant that was virtually free of pollutants and carbon emissions. There were no smokestacks at San Onofre. Eighteen square miles of solar panels would be needed to duplicate the amount of clean power that was generated by San Onofre's two units.
San Onofre produced 19 percent of the power used by Southern California Edison (SCE) customers. Nuclear power provides roughly 20 percent of all U.S. electricity and is the nation's No. 1 source of emission-free electricity.