The blackouts happened over a roughly hour-long period, beginning shortly before 9:30 a.m., and initially affected about 13,000 addresses, according to San Diego Gas & Electric.
The affected locations included the College area, Hillcrest, Kensington, Mission Hills, Normal Heights, North Park, Old Town, Talmadge and University Heights.
By late afternoon, utility crews had restored power to all but about 1,100 customers in City Heights, Chollas Creek and Oak Park, SDG&E reported. The remainder were expected to be back in service by early evening.
A summer heat wave is expected to send temperatures soaring in inland San Diego County Thursday through the weekend.