The outage, which affected around 575 customers in Potrero Hill, was first reported at around 8:30 a.m., spokesman Joe Molica said.
One of the workers who responded to the neighborhood was injured when a transformer failed during an initial investigation, Molica said.
The worker suffered minor burns and was taken to a hospital, Molica said. He is expected to recover.
PG&E was working to replace the transformer and will conduct a thorough investigation into the incident, Molica said.
Power had been restored to all but a few dozen customers by 1 p.m.
