San Diego Gas & Electric was ordered by state regulators to cut electricity to 115,000 customers for several hours Sunday.
The outage occurred just after 1 p.m. and covered the county from Mission Valley north to San Clemente. As of 3 p.m., SDG&E reported all outages had been restored.
SDG&E gave no notice to customers before the power was cut, forcing many businesses to close Some businesses say they had at least a thousand dollars in losses.
The outage was the result of the California Independent Systems Operator ordering SDG&E to drop 150 megawatts of load in their service territory immediately around 1:15 p.m, SDG&E said. Eleven minutes later the power was cut.
They reduced power due to an unexpected loss of generation, said SDG&E spokeswoman Cathleen Romero said. That resulted in short outages scattered throughout the county.
California Assemblymember Toni Atkins, however, said there was a problem at the Otay Power Plant.
In May, SDG&E said it would have enough resources to meet the summer power demand.
The outages come amid record-breaking heat across San Diego County. Montgomery Field's previous record of 87 was broken earlier Sunday when temperatures were recorded as high as 96.
SDG&E calls the incident very rare and says they do expect it to happen again anytime soon.