With strong winds blowing and bone-dry conditions, utility officials in San Diego on Thursday began shutting off the power to thousands of people — a pre-emptive move to reduce the danger of power lines sparking wildfires.

It’s a controversial approach that may soon become a growing trend across California.

As huge fires continued to envelope parts of Los Angeles and Ventura counties, San Diego Gas & Electric cut electricity to 12,000 customers in San Diego County by Thursday afternoon, after Santa Ana winds reached 88 mph in some rural areas.

Even though no fires were burning in San Diego County on Thursday morning, the utility notified up to 170,000 customers that they could have their power shut off by Saturday as a safety precaution, and that electricity in some affected communities wouldn’t be back on until Monday.

“We recognize the inconvenience to our customers and appreciate their patience,” said Joe Britton, a spokesman for San Diego Gas & Electric “We are doing it for public safety. We need to protect the public.”

Get top headlines in your inbox every afternoon. Get the free PM Report newsletter.

With the number of fires in the West growing due to climate change, and a recent decision by the state Public Utilities Commission to require that a utility — not ratepayers — pick up the costs for fires caused by its power lines, it’s likely that Californians are going to see more deliberate, pre-planned power outages when there is extreme wildfire risk, experts say.

“The utilities are damned if they do, damned if they don’t,” said Frank Wolak, a Stanford University economics professor who has studied energy issues extensively.

Trees falling into power lines or wires blowing off power poles can spark fires that can kill dozens of people and level entire neighborhoods, so turning off the power amid extreme conditions — high temperatures, low humidity and strong winds — is a logical tool to reduce risk, Wolak said, but it also creates major headaches.

“It certainly seems that it is a reasonable response,” Wolak said, “but consumers are going to face no electricity, and that has many unintended consequences that will likely only be known after the fact.”

Among the problems from planned blackouts: Food in refrigerators can go bad. Stores have to close. Traffic lights, elevators and garage-door openers don’t work. Medical equipment that elderly or infirm people might have at home, like respirators, can shut down. People who work from home can lose power to their computers. Water pumps may not work.

Wolak said the solution is probably to harden the power grid. That would require such measures as replacing wooden poles with steel poles, better insulating power lines, and in some places, burying lines, which is very expensive. Those costs would all be passed along to ratepayers, he noted, but that may be part of society’s cost of adjusting to climate change, similar to the cost of building stronger levees and sea walls as sea levels continue to rise.

“Customers and politicians have to recognize that in a world where fires and other extreme weather events are going to be more severe, that argues in favor of building a more robust system, and that costs money,” Wolak said.

With huge fires raging in Los Angeles and Ventura, around 11 a.m., Thursday, a fire began in northern San Diego County in Fallbrook, near Camp Pendleton, and had burned 2,500 acres by mid-afternoon. The fire forced the evacuation of two schools and the closure of two lanes of Interstate 15 in an area where San Diego Gas & Electric had not shut off power beforehand.

California has seen the problem of wildfires caused by power lines take center stage in recent months.

In one of the worst disasters in modern California history, a series of fires that began Oct. 8 in Napa, Sonoma, Mendocino and other Northern California counties burned more than 245,000 acres, destroyed 8,900 homes and killed 44 people.

Cal Fire has not yet determined how the blazes started, but investigators are looking at whether power lines owned by PG&E were at fault for some of the fires, stoked by windy conditions. The utility has told investors it faces massive liabilities if it is found to have caused the fires, and on Wednesday State Insurance Commissioner Dave Jones said insured losses from the fires so far total $9 billion.

Records released Wednesday by the state Public Utilities Commission showed that PG&E does not have a policy for pre-emptively turning off power lines during dry and windy conditions to reduce fire risk, and PG&E did not do that in the Northern California communities that burned in October before those fires began. In a response to PUC questions on Oct. 17, PG&E officials said “de-energizing lines can have an immediate and very broad impact on public safety.”

PG&E officials added that it “can affect first responders and the operation of critical facilities such as hospitals, the provision of water and other essential services, street lights and signals, communications systems, operation of building systems such as elevators, and much more.”

Meanwhile, financial risk to the utilities is rising. Last week, the PUC rejected a request from San Diego Gas & Electric to recover $379 million from its ratepayers after investigators found its power lines sparked three huge fires in 2007. By a 5-0 vote, the commissioners said that the San Diego utility had not operated its electrical system in a “reasonable and prudent” manner when the fires began, as state law requires.

As a result, the commissioners ruled, San Diego Gas & Electric’s shareholders, not its customers, must absorb the costs. That ruling sent shock waves across the utility industry.

Related Articles California firefighter who died in blaze started by gender-reveal party was on elite Hotshot crew

Smoke from California fires may have killed more than 1,000 people

Where Bobcat fire fits among LA County’s largest wildfires of past century

Bobcat fire surpasses 110,000 acres, as firefighters continue to protect neighborhoods

Skelton: To study wildfire prevention, Newsom should look to Baja After the 2007 fires, San Diego Gas & Electric asked the PUC for permission to shut down some power lines during dry, windy conditions to reduce fire risk. Disability groups said they wanted customers to be notified in advance so they could prepare. The PUC, in a 2012 ruling, granted the utility the authority to shut off power ahead of time, but “only as a last resort, and only when SDG&E is convinced there is a significant risk that strong Santa Ana winds will topple power lines onto flammable vegetation.” The PUC required the utility to notify the public ahead of time, and to file a report to the PUC detailing wind, temperature, humidity and other conditions to see if the act was justified.

Consumer groups — who want to keep costs low and improve safety — are still struggling to come up with a position on the issue.

“We’re still studying the issue,” said Mindy Spatt, a spokeswoman for The Utility Reform Network, a San Francisco nonprofit group. “We don’t know enough yet about how this will impact the customers to know whether or not it is a good approach.”

Staff writer Matthias Gafni contributed to this report.