A one-alarm fire at one of PG&E’s key substations in San Francisco this morning looks like the cause of the blackout that’s currently affecting over 125,000 SF residents.
With tens of thousands of people still without power in San Francisco, SF Mayor Daniel Lurie, in tandem with SFMTA and SF Department of Emergency Management, has advised people to effectively shelter inside amid ongoing blackouts, only leaving their homes for necessary travel. The Mayor and City departments are encouraging residents to check in on one another in safe ways.
Muni lines and traffic signals are impacted by the power outage. If you don’t need to travel tonight, please stay off the roads and stay inside.
We will be expanding officer presence at intersections and corridors to ensure the safety of those still on the road.
We remain in… pic.twitter.com/Q30y3SPXa9
— Daniel Lurie 丹尼爾·羅偉 (@DanielLurie) December 21, 2025
Amid the PSA announcements from PG&E and the City government, particularly the emergency management department, the San Francisco Fire Department has kept the public up-to-date on the one-alarm fire at PG&E’s substation on 8th and Mission Streets that was first reported this morning at 10 a.m. — just as certain SF zipcodes began losing power.
And it appears it’s this fire that’s responsible for SF’s massive blackout (or, at the very least, was the catalyst for the power outages that began falling like dominoes earlier today).
SFFD is on scene of a 1 alarm fire at a PG&E substation located at 8th St. and Mission St. we are working collaboratively to shut shut down power and extinguish the fire with carbon dioxide. Please avoid the area , Heavy traffic. #sffd pic.twitter.com/1CmcK0CTIW
— SAN FRANCISCO FIRE DEPARTMENT MEDIA (@SFFDPIO) December 20, 2025
“SFFD is on scene of a 1 alarm fire at a PG&E substation located at 8th St. and Mission St.,” reads a post on X from the City fire department. “We are working collaboratively to shut down power and extinguish the fire with carbon dioxide. Please avoid the area. Heavy traffic.”
Utility substations are integral to electrical grid systems, responsible for amplifying voltage, controlling electrical flow between stations, and playing necessary roles in controlling circuit switches between controllers and the grid system, effectively moving power to and from sectors based on efficiency and needs. Think of substations like traffic lights: These posts direct electrical energy flow in high-congestion areas, allowing traffic — in this case, electrons — to either continue moving forward or stop to avoid unnecessary traffic jams.
(Substations, too, are responsible for safeguarding grid systems from unchecked voltage faults that could otherwise hobble an entire grid system.)
We’re experiencing citywide power outages. Please stay home if you can, avoid all unnecessary travel, and check on neighbors safely. Updates on service and restoration times are available via PG&E: https://t.co/DthlRd2zLd
If you are home without power:
🔦Check in with neighbors,… pic.twitter.com/6aOo8uotf6— San Francisco Department of Emergency Management (@SF_emergency) December 21, 2025
San Francisco is home to about 30 substations operated by PG&E, nine of which are considered key or essential to providing SF with power. As inference would have it (and suggests), one of those keystone substations is located at 8th and Mission streets.
With this substation damaged — burned, in fact — it’s unclear how its duties will be distributed across SF’s PG&E grid without overloading other substations, assuming it can’t be repaired.
As of 7 p.m. Saturday, December 20th, large swaths of San Francisco still remain without power, affecting at least 130,000 residents.
