On San Francisco’s Yukon Street, a nub of a road tucked into the hillside below Market Street near Twin Peaks, the sounds of passing cars provide the neighborhood’s ambient soundtrack on any given night.
But when a transformer on that street blew up Tuesday night, the relative quiet was disrupted by an explosion that could be heard and felt in neighborhoods as far away as Potrero Hill.
At 10:14 p.m., a fireball that appeared to be several stories high shot into the sky, and the area surrounding the Kite Hill Open Space went dark.
About 15 minutes later, fire trucks snaked up the hillside to Yukon Street, near where Market Street becomes Portola Drive.
Fire spokeswoman Mindy Talmadge said that multiple callers, both on Yukon Street and in other neighborhoods, reported a small fire and that firefighters initially had trouble finding the blaze.
Talmadge said that a unit was dispatched at 10:18 p.m. and arrived at Christmas Tree Place — atop Twin Peaks — four minutes later. At that time, a backup unit was dispatched to the area of 20th and Douglass streets, several blocks downhill from Yukon Street.
The crews eventually found the fire, and extinguished the flames at 11:01 p.m. after PG&E de-energized the transformer, Talmadge said.
PG&E also dispatched crews to the neighborhood to respond to reports of a power outage, and Talmadge said the incident was treated as a joint response once it was determined that the fire involved a pole-mounted transformer.
Roughly 275 PG&E customers lost power because of the equipment failure, according to a PG&E spokesman. The utility is still investigating what caused the problem.
“Typically these types of failures occur when there’s a spike in power demand,” PG&E spokesman Jason King said this morning.
That spike in demand, King said, can be caused by the introduction of a power-hungry device, such as an electric car, equipment for a home office or an indoor grow operation.
He urged customers to alert PG&E if they plan to use a device that needs that much power so that the company can anticipate increases in demand.
An electric car can require as much as three households worth of energy, King said, which he said is why PG&E works with electric car dealers so that it is notified when customers bring new cars on the grid.
As of this morning, PG&E had not yet identified what caused the failure.
King did not have information about the age of the equipment or frequency of such failures.
“They’re not a common occurrence, but they do happen,” he said.
Power was restored to all but 58 customers at 4 a.m., and was fully restored by 6:05 a.m., King said.