The utility made the announcement a day after a large swath of the Southwest and parts of Mexico lost electricity, and restoration of power came sooner than expected.
Most of the people affected were San Diego Gas & Electric customers.
Officials at Phoenix-based Arizona Public Service Co. says the outage occurred after an electrical worker removed a piece of monitoring equipment at a substation.
The blackout also caused a sewage spill that closed some San Diego-area beaches. All public schools in the city also are closed Friday as well as local state universities and community colleges.
It's still unclear how many power customers elsewhere are still without power.