SAN FRANCISCO (KRON) -- A widespread power outage in San Francisco Friday left thousands of customers without power. PGE's outage map indicates the outage was impacting customers in the Inner Sunset, Upper-Market and Castro districts. Bay Bridge lights to return Friday night in grand lighting cerem ony According to PGE, there are around 6,383 impacted customers as of 2:59 p.m. A crew is working to restore power with an estimated time of restoration for 8:15 p.m. "PGE has established that an electrical equipment failure in an underground vault at 18th and Guerrero was a cause of outages impacting San Francisco customers this afternoon," PGE said in an update to KRON4. As of 5 p.m., approximately 3,100 customers remain without power, according to PGE. Photo: PGE PGE said the outage, which comes on the last day of an unprecedented, five-day March heat wave, was unplanned. "A large, unplanned power outage is impacting multiple neighborhoods and moving throughout the city," the San Francisco Department of Emergency Services said in a tweet. ...read more read less