The power failure, which affected more than 370,000 households and businesses, halted trading at the Pacific Stock Exchange, briefly dimmed lights on the Golden Gate Bridge and caused some of the worst chaos seen in the area since the 1989 earthquake.
"I've lived in the Bay Area for three decades and I've never seen anything like this," said Chris Johnson, a spokesman for the Pacific Gas and Electric Company (PG&E).
Gordon Smith, the company's president and chief executive officer, said the blackout had been traced to "simple human error" at an electricity substation in San Mateo County, south of San Francisco.
Workers adjusting lines turned power on without proper grounding, Mr Smith said. That sparked a domino effect, which shut down two San Francisco sub-stations and pulled the plug on most of the city and its southern suburbs.
PG&E officials said staffwere manually checking sub-stations around the San Francisco area, and hoped to have power restored by yesterday afternoon local time.
The power failure brought public transport to a halt, and officials at San Francisco international airport said the staff had been forced to turn to emergency auxiliary power for much of the morning. Traffic lights around San Francisco blinked out at the height of rush hour, leaving traffic snarled and halting the city's electrical bus system. Dozens of people were trapped in lifts in office blocks.
Some commentators noted that the city was well prepared to deal with the power failure because of its history with earthquakes, and that essential services such as hospitals were able to maintain a skeleton service by using emergency generators.
"All the rehearsals and all the preparations and all the trial runs have now paid dividends," Mayor Willie Brown said. "San Franciscans have been performing magnificently ... road rage has been totally removed, people have been incredibly courteous to each other."
Police reported no incidents of looting, and only one person was injured in an accident that could be attributed to the morning's traffic chaos.
In the main shopping area, however, department stores kept their doors closed because neither lights nor cash registers would work, while the city's cable cars disappointed tourists by stopping in their tracks.
The Pacific Stock Exchange halted all trading after phones and computers shut off. A spokeswoman said the power failure could cost the exchange millions of dollars in lost business.
As the power blackout stretched into the afternoon, many commuters began heading back out of the city, figuring their offices were effectively closed for the day. (Reuters)Reuse content