Mission Substation outage traced to moisture contamination and arc-flash fire
Updated
Updated · KGO-TV · May 8
Mission Substation outage traced to moisture contamination and arc-flash fire
8 articles · Updated · KGO-TV · May 8
The 77-page Exponent report said the 20 December failure at PG&E's San Francisco facility cut power to 120,000 customers after equipment failed.
Investigators found PG&E had seen damage to the insulating board in November, while humidity, moisture and water-saturated ventilation filters left the switchgear room poorly protected.
PG&E said it took immediate corrective steps and will use the findings to improve reliability, as businesses reported losses and local officials questioned whether the blackout was preventable.
San Francisco has debated a public utility for decades. Is this blackout the final push to end its reliance on PG&E?
With soaring profits and a failing grid, what will force utilities to prioritize infrastructure over shareholder returns?
Modern grid technology can prevent these failures. Why are cities still hostage to breakdowns of 1940s-era infrastructure?
The December 2025 San Francisco Blackout: Causes, Consequences, and the Push for Grid Reform
Overview
On December 20, 2025, a major power outage struck San Francisco when a fire broke out at PG&E’s Mission substation, initially affecting 40,000 customers. As firefighters worked to control the blaze and crews de-energized more areas for safety, the blackout expanded to impact about 130,000 people. The fire caused serious equipment damage and complicated emergency response efforts. This incident highlighted vulnerabilities in PG&E’s aging infrastructure and raised concerns about maintenance and communication. The event underscored the need for urgent improvements to ensure reliable power and better crisis management for the city’s future.