One major utility began cutting power Wednesday to millions of Californians due to predicted high winds that could down power lines and spark wildfires. And other power companies warned they could follow suit.
Here's what you need to know.
Though utilities have warned for months that preemptive cutoffs were a possibility, the outages appeared to be catching many consumers by surprise. While many Florida and East Coast residents have long learned to cope with power outages from hurricanes, weather-related outages could be considered a new phenomenon in the Golden State.
The website for Pacific Gas & Electric, serving Northern and Central California, was swamped by those seeking more information, and many customers complained the pages couldn't be accessed. Likewise, Southern California Edison customers were having trouble accessing the power-outage section of its website.
With that in mind, here are some answers to key questions.
Where are the outages now and where will they be?
PG&E began shutting off power Wednesday morning, cutting off 500,000 homes and businesses in Northern California. It planned to expand its actions in the evening to parts of the Bay Area including San Jose and Santa Cruz.
More: 'PG&E clearly hasn't made its system safe.' California lawmakers slam utility amid widespread power outage
Farther south, where gusty Santa Ana winds weren't expected until early Thursday, Southern California Edison announced it may turn off power to more than 170,000 customers in its 50,000-square-mile service area. It includes at least 49,024 in the northern reaches of Los Angeles County and 20,449 in Ventura County.
San Diego Gas & Electric said it is prepared to cut power to 28,701 customers, with most of the communities affected in inland areas.
Because a single customer account can serve a household or business, the estimated number of people without power was expected to reach 2 million.
If they haven't already, when will they cut my power?
There is no set time. Utilities plan to make the calls based on conditions - wind speed is not the only factor.
Southern California Edison said it will also take into account humidity and ground observations before cutting power. It'll be a judgment call.
Why is this happening?
Power lines were blamed for sparking the Camp Fire nearly a year ago that killed 85 people, blackened 153,000 acres and destroyed 14,000 structures in Northern California. The town of Paradise, population 26,800 as of 2010, was so devastated that only 2,034 residents were left by April.
PG&E filed for bankruptcy after a cascade of lawsuits arising from the fires. To avoid being blamed for another conflagration and having to shoulder massive payouts due to fires from downed lines, utilities have decided to cut power during high-wind episodes.
How long will the power be out?
Unclear. It could be hours or could be days, based on conditions.
What can I do about it?
Home Depot reports a brisk business in selling gasoline-powered generators and other supplies.
"Our stores have been busy with customers coming in to purchase emergency items like gas cans, lanterns, batteries, cell phone chargers and generators. Our merchandising and supply chain teams are working hard to replenish these important items as quickly as possible to best serve customers," said spokeswoman Margaret Smith.
Competing home center chain Lowe's also reported "strong demand" and reported to have stocked up in advance.
"We have 35 stores in the areas affected by the outage and our Emergency Command Center has shipped more than a dozen truckloads of generators, water, flashlights, lanterns, batteries and other supplies to help these communities during the outage," said spokesman Steve Salazar.
More: More than 1 million in California are without power in preemptive shutdown to combat wildfires
A gas-powered generator can keep a refrigerator alive during a power outage, but may not be able to power a whole house or business. For those kinds of installations, electricians have been busy for months adding backup power to businesses that knew blackouts could be coming, said Greg Armstrong, executive director of the Northern California Chapter of the National Electrical Contractors Association.
Southern California Edison warns that generators need to be placed outdoors and rigged to individual appliances with a heavy-duty extension cord. Connecting generators directly to household circuits can create danger for the utility's repair crews in the form of dangerous "backfeed."
Many schools and some universities were closing due the power outages. Motorists were topping off their cars' tanks ahead of a possible shutdown of gas stations if they lose power. Some grocery stores were jammed ahead of the shutdowns.
Hospitals remained open using their backup generators. But some, like the San Ramon Regional Medical Center, were weighing whether to divert ambulances to other facilities in areas not affected by outages.
For those on the road, be careful: Traffic signals may be out. That means four-way stops at intersections.
Some events may be affected. Directors of the annual film festival in Mill Valley, a bucolic Marin County town north of San Francisco that's in the potential blackout zone, preventively moved Wednesday's screenings to neighboring Corte Madera.
More: California power outages aim to reduce risk of wildfires caused by dry and windy weather
Can a homeowner with solar panels just use their own power?
In many cases, no. Almost all home solar systems are tied into the local power company's power grid, so customers can feed solar back into the system and get compensated for the electricity their solar panels produce.
These systems are designed to turn off when utility power is out. This is for the safety of electrical workers who may be working on the grid near a home during an outage. Having power flowing into the system could kill them.
To be able to access your solar power in a shutoff, you would need to have a solar inverter installed as part of your system. "These inverters are quite common today," said Lior Handelsman, vice president of marketing for SolarEdge.
So if you've got solar panels, it doesn't do you any good when the power's out?
It does if you have a home battery attached to your solar energy system. Then you can keep the lights on during a utility blackout. The solar energy powers the home during the day and any excess energy is used to charge the battery. The battery can then be used at night, or when the grid goes down.
For example, Sunrun, a San Francisco-based solar company, sells the Brightbox battery, which provides backup power to four circuit breakers for approximately 8 to 12 hours at night. Most customers connect it to their refrigerator, several rooms of lights and devices such as WiFi and their garage door openers, the company said.
What about people with electric cars?
Unless they have a solar panel installation with a battery, they won't be able to charge during power outages. However, most electric vehicles today have a range of between 100 to 250 miles between charges, so if they're fully charged, they can often outlast power outages.
Contributing: Elizabeth Weise, Marco della Cava, Robert Hanashiro, Michele Chandler, Gabrielle Paluch, Cheri Carlson and Associated Press
This article originally appeared on USA TODAY: Power outage Q&A: What California needs to know about the cutoffs