The power failure, which at its height affected 88,000 customers, struck just after 9 a.m. and extended through the Tenderloin and Chinatown, up Nob Hill, and into the Marina and the Presidio. But as the evening commute began at 4 p.m., there was finally good news: Power had been restored to all but about 3,000 customers. An hour later, everyone had power.

While no major injuries were reported, the ordeal meant everything from lost business at shuttered shops in Union Square to minor shake-ups for those briefly trapped by darkness in the bowels of downtown skyscrapers.

Firefighters responded to more than 100 calls for service in the Financial District and beyond, including 20 elevators with people stuck inside. Everywhere, sirens blared as engines maneuvered along streets jammed with traffic. Hospitals, though, were operating on backup power, with most surgeries and other procedures continuing.