San Francisco ground to a near halt on Saturday after a sudden and widespread power outage plunged large parts of the city into darkness, disrupting transportation, shuttering businesses, and snarling traffic at one of the most critical retail moments of the year. The blackout affected roughly 130,000 homes and businesses, according to utility provider Pacific Gas and Electric Company, in a city of just over 800,000 people.

As officials worked through the night to restore electricity, questions quickly followed. What triggered the outage? Why did it spread so widely? And what does it reveal about the resilience of San Francisco’s aging power infrastructure?

What exactly happened during the San Francisco power outage?

The outage began shortly after 1 pm on Saturday, catching residents and city services off guard. Traffic signals failed across multiple neighborhoods, public transport services were disrupted, and commercial districts went unusually quiet for a peak holiday shopping weekend.

Pacific Gas and Electric Company confirmed that approximately 130,000 customers lost power within a short span of time. While electricity was restored to most by early Sunday morning, around 21,000 customers were still without service hours later.

The scale and speed of the outage made it one of the most significant power disruptions San Francisco has experienced in recent years.

What caused the massive power outage in San Francisco?

City officials traced the outage to a fire at a PG&E electrical substation near the intersection of 8th and Mission streets, a critical node in the city’s power distribution network.

According to PG&E, the fire caused “significant and extensive” damage to substation equipment, triggering cascading failures across multiple neighborhoods. Substations act as hubs that regulate voltage and distribute electricity to large sections of the city. When one fails suddenly, the effects can ripple outward far beyond the immediate area.

Key factors that contributed to the widespread outage included:

• Damage to multiple components within the substation
• Automatic safety shutdowns designed to prevent further equipment failure
• Heavy load conditions typical of winter weekends and holiday shopping periods

Investigations into what caused the fire itself are ongoing, and officials have not yet said whether equipment failure, external factors, or human error played a role.

How extensive was the impact across the city?

The blackout disrupted nearly every aspect of daily life in San Francisco.

Traffic and public safety challenges

With traffic lights out across wide areas of the city, police officers were dispatched to manually control major intersections. The Department of Emergency Management urged residents to avoid non-essential travel and reminded drivers to treat dark signals as four-way stops.

Despite these efforts, congestion quickly built up, especially in downtown corridors and commercial zones.

Public transport disruptions

Public transit systems were also affected:

• Trains on parts of the city’s rapid transit network bypassed several downtown stations
• Bus services faced delays due to gridlocked streets
• Self-driving ride-hailing services operated by Waymo were temporarily suspended as a safety precaution

For many residents, the outage turned routine weekend travel into a slow and frustrating ordeal.

Businesses forced to close

Retailers and restaurants bore the brunt of the disruption. With Christmas just days away, many businesses were relying on weekend foot traffic to meet end-of-year sales targets. Instead, storefronts went dark, point-of-sale systems failed, and perishable inventory was at risk.

The San Francisco Chronicle quoted business owners who described the sudden loss of customers as devastating, particularly because parts of the city were also shrouded in fog, further discouraging shoppers.

How quickly was power restored, and why did some areas wait longer?

By early Sunday morning, PG&E reported that electricity had been restored to about 110,000 customers. However, roughly 21,000 homes and businesses remained without power, with no precise timeline given for full restoration.

PG&E said repairs were complex due to the extent of the damage at the substation. In cases like this, crews must:

• Inspect damaged equipment to ensure it is safe to re-energize
• Replace or repair transformers and control systems
• Gradually bring sections of the grid back online to avoid overloads

The utility mobilized additional engineers and electricians from across the region to speed up the process.

What did city leaders and PG&E say about the outage?

Mayor Daniel Lurie acknowledged the disruption and frustration felt across the city, calling it a “rough day” for San Francisco. Speaking from the emergency operations center, he said city agencies were coordinating closely with PG&E and first responders to manage traffic, ensure public safety, and restore normal services as quickly as possible.

PG&E emphasized that the grid had been stabilized by Saturday evening and said it did not expect further outages related to the incident. The company also confirmed that there were no reports of injuries linked to the substation fire.

Why do substation fires cause such widespread blackouts?

Substations are among the most critical and vulnerable parts of the power grid. Unlike transmission lines, which often have built-in redundancies, substations can represent single points of failure for large geographic areas.

When a substation fire occurs:

• Power must be cut immediately to prevent further damage
• Backup routing may not have sufficient capacity for full demand
• Restarting equipment requires careful testing to avoid additional failures

In dense urban environments like San Francisco, where infrastructure is tightly packed and demand is high, the margin for error is small.

Is San Francisco’s power infrastructure especially vulnerable?

The outage has renewed scrutiny of San Francisco’s electrical infrastructure, much of which dates back decades. While PG&E has invested billions in grid modernization and wildfire prevention across California, urban substations remain challenging to upgrade due to space constraints and regulatory complexity.

Experts often point to several structural risks:

• Aging equipment operating near capacity
• Increased electricity demand from electric vehicles and data centers
• Climate-related stresses, including heat waves and extreme weather

Although this outage was not directly linked to extreme weather, it highlights how a single failure can cascade through a modern city.

What are the economic consequences of holiday weekend outages?

Timing matters. This blackout hit during one of the busiest shopping weekends of the year, amplifying its economic impact.

For small businesses, even a single lost day in December can have outsized consequences. Restaurants lost reservations, retailers missed sales, and hourly workers lost shifts. While some losses may be partially recovered, others are permanent.

Urban economists often note that outages during peak commercial periods can ripple through local economies for weeks.

What happens next as investigations continue?

Investigators are still examining the cause of the substation fire. Key questions include:

• Whether equipment failure or maintenance issues played a role
• If external factors, such as construction or environmental conditions, contributed
• Whether additional safeguards could have limited the spread of the outage

Findings from the investigation could influence future safety protocols and infrastructure investments.

TL;DR

A fire at a PG&E substation near 8th and Mission streets triggered a massive power outage that affected around 130,000 homes and businesses across San Francisco. The blackout disrupted traffic, public transport, and holiday shopping during a critical weekend. While most power was restored by early Sunday, the incident has raised fresh concerns about infrastructure resilience and the risks of single-point failures in dense cities.