Nearly 8,700 SDG&E customers in Rancho Bernardo and Poway lost power on Wednesday, Sept. 9, during the largest single outage in a day that broke the utility's all-time electricity demand record.
The outage struck around 1:30 p.m. and affected residents in Poway, Rancho Bernardo, Rancho Peñasquitos, 4S Ranch, San Pasqual, Del Dios and Lake Hodges, Fox 5 San Diego reported. By 3 p.m., most customers had power restored, though about 280 remained in the dark. As of Thursday, Sept. 10, around 6:30 a.m., 128 customers were still without electricity.
SDG&E said the cause remains under investigation.
The local outage was one of 29 unplanned outages across SDG&E's service territory over a 24-hour stretch from midnight Sept. 8 through midnight Sept. 9, the San Diego Union-Tribune reported. Those outages knocked out power to nearly 15,000 customers total. The Rancho Bernardo/Poway outage, involving circuit lines, accounted for more than half of that total.
The outages came as SDG&E hit a peak net system load of 5,209 megawatts on Sept. 9, surpassing the previous record of 4,890 megawatts set in September 2014. SDG&E serves about 1.3 million customers.
Warm overnight temperatures played a role. SDG&E spokesperson Alex Welling told the Union-Tribune that the overnight low at Montgomery-Gibbs Executive Airport in Kearny Mesa dropped to only 79 degrees between the evening of Sept. 8 and early hours of Sept. 9. The typical high for that time of year is 82.
"When we have those warm temperatures overnight, and people are running their ACs, it doesn't allow the system to cool down," Welling said. "So it puts that excess strain on the system, which can cause unplanned outages."
The heat wave, fueled in part by the remnants of Hurricane Marie, pushed daytime highs to 106 degrees in the San Pasqual Valley, 102 in Ramona and El Cajon, and 98 at Marine Corps Air Station Miramar, according to a separate Union-Tribune report on Sept. 8. The prolonged heat also elevated wildfire risk countywide.
Statewide, the California Independent System Operator (CAISO) reached its highest single-day demand of 2026 on Sept. 9, according to the Union-Tribune. CAISO did not issue a Flex Alert, a voluntary conservation request, in part because California's power system has added about 31,000 megawatts of capacity over the past six years. Locally, SDG&E has added 2,466 megawatts of new capacity in that same period, according to an SDG&E statement released Monday, Sept. 14.
Kevin Geraghty, SDG&E's chief operating and safety officer, said in the statement that crews worked in extreme conditions to serve their communities.
SDG&E advises customers to pre-cool their homes before 4 to 9 p.m., when statewide electricity rates are highest. Customers can explore bill assistance and energy-saving resources at sdge.com/simplesteps.
