Two retired power plants owned by AES Corp. could be turned on this summer to help California’s electrical grid avoid power interruptions in San Diego in the event of a prolonged outage at both San Onofre nuclear reactors, staff of the grid operator said on Thursday.

The staff of the California Independent System Operator told the board it has evaluated the impact of running Units 3 and 4 at the Huntington Beach natural gas-fired plant along with accelerating two transmission projects and utilizing more conservation efforts to deal with the potential loss of the 2,150-megawatt San Onofre Nuclear Generating Station.

Both San Onofre nuclear units have been shut since January due to premature wear found on tubes in massive steam generators and operators are not saying when the units might be able to restart.

Recalling the Huntington units, which AES retired at the end of 2011, would add 450 megawatts of generation in Southern California and bolster the transmission system to allow power from outside the state to flow to San Diego, said Neil Millar, the ISO’s executive director of infrastructure development.

“It’s not only San Diego, but southern Orange County that is at risk without mitigation,” Millar said.