Report says PG&E saw warning signs before San Francisco blackout

Engineers had already flagged damaged equipment, water and ventilation problems at a San Francisco substation before a December fire knocked out power for more than 130,000 people, cutting directly against PG&E’s public claim that there were no prior warning signs.

The new report puts the utility’s timeline under a harsher light. It says the problems were identified before the blackout that left about 120,000 San Francisco residents in the dark, and that the outage was not a routine interruption but part of a substation fire that cascaded into a much larger citywide failure. PG&E has since revealed the cause of the substation fire, adding another layer to a dispute that now centers on what the company knew, when it knew it and why the risks were not addressed sooner.

San Francisco supervisors pressed PG&E executives on those questions during a three-hour hearing over the December outage. The hearing focused on the blackouts that rippled across the city, knocked out traffic signals in some areas and disrupted daily life in one of the country’s densest urban centers. The mismatch between the utility’s assurances and the new report’s findings has intensified scrutiny of Pacific Gas and Electric Co., which has faced repeated criticism in California over how it manages aging infrastructure.

City leaders have already escalated the matter beyond the hearing room. San Francisco officials wrote to the head of PG&E’s parent company seeking a formal state investigation into the substation fire and the blackouts that followed. The move signals that the city wants not just an explanation of this incident, but a broader examination of whether similar hazards could still threaten other critical equipment serving San Francisco County.

The stakes are high because PG&E’s safety record remains a defining part of the backdrop. The company’s history includes the 2010 San Bruno pipeline disaster, after which investigators and courts found evidence that PG&E ignored or concealed hazards. That history has made every new allegation of overlooked danger harder for the utility to dismiss, especially when the failure reaches deep into San Francisco’s everyday systems.

For a city that has already endured outages that shut off power to thousands and scrambled traffic signals, the December blackout was more than an inconvenience. It became a test of whether PG&E can prove it is seeing the warning signs before the lights go out.