Edison International's announcement came as the U.S. Nuclear Regulatory Commission said it will hold a public hearing on the plant's operation June 18 in San Juan Capistrano, the Los Angeles Times reported Thursday.
The plant was shut down in January. An NRC inspection team began work in March to look for the cause of unusual wear in tubes in the steam generators.
Victor Dricks, an NRC spokesman, said the June 18 meeting will include a preliminary report on the tubes.
Ted Craver, a spokesman for Southern California Edison, said the company will not be able to submit a restart plan until the end of July. He said the NRC would then need about a month to review it.
While Unit 2 might restart in September, Unit 3 could remain out of service longer.
The San Onofre plant produces almost 20 percent of Southern California Edison's power when it is at full operation. The company is a subsidiary of Edison International.