California power company Pacific Gas and Electric (PG&E) cut power Wednesday to millions of Californians due to high winds that could down power lines sparking wildfires.

Utilities companies have warned for months that cutoffs were possible, but the power cut seems to have caught many by surprise.

Twitter was buzzing with comments about the outage from consumers in the Northern California area. Many posted angry tweets about the power company's website, serving Northern and Central California, being down and making updates on the cuts inaccessible.

While many East Coast residents have learned to cope with power outages from hurricanes, weather-related outages are a relatively new phenomenon in California.

Where are the outages?

PG&E began shutting off power Wednesday morning. Nearly 500,000 homes and businesses in Northern California were without power and by midday it expanded to parts of the Bay Area, including San Jose and Santa Cruz.

Farther south, where Santa Ana winds weren't expected until early Thursday, Southern California Edison said it might cut power to more than 170,000 customers. It included more than 50,000 in northern Los Angeles County and nearly 20,449 in Ventura County.

San Diego Gas & Electric also said it could cut power to nearly 30,000.

The reason for power cuts

Power lines were to blame for setting off fires nearly a year ago in Northern California that killed 86 people and burned 62 hectares. The town of Paradise was so devastated by the January fire that, by mid-July, only 2,034 residents - of nearly 27,000 before the fire - were living in the city.

PG&E filed for bankruptcy earlier this year after the utility was found liable for igniting multiple fires. In September, PG&E reached an $11 billion settlement in those claims. A third group of claims is still working its way through state and federal courts.

To avoid more legal fights, PG&E and other utilities companies decided to cut power during high-wind episodes. Based on conditions, power cuts could last up to six days.

Gas-powered generators are flying off the shelves at stores, and electricians are busy installing backup power to businesses that knew blackouts could be coming.

Southern California Edison warned 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, they said.

Many schools and universities were closing due the power outages. People were filling their gas tanks in case gas stations lost power. There were also long lines reported at grocery stores ahead of the shutdowns.

Hospitals remained open, using backup generators. But some, like the San Ramon Regional Medical Center, were weighing whether to divert ambulances to other hospitals not affected by outages.

Solar power

Almost all home solar systems are tied into the local power company's power grid, so the customer can feed solar back into the system and get paid for the electricity their solar panels produce.

But these systems are turned off when utility power is out. That is to keep electrical workers who are working on the grids safe because power flowing into the system could kill them.

This leaves many homes using solar power without electricity. But residents who have a home battery attached to their energy systems are in luck. 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.

The same is true for electric cars. If the cars have a solar panel with a battery, they will likely have a range of between 160 to 400 kilometers between charges. So if they're fully charged, they can often outlast power outages.

Climate change, years of drought, and the construction of houses and communities in wildland areas have all contributed to the spate of intense and deadly fires in California in recent years, experts say.