Pacific Gas & Electric (PG&E) initiated the precautionary blackout on Saturday - expected to be the largest in state history - due to forecasts of extreme winds, which it said could damage facilities and cause new fires, the BBC reported.
PG&E said the powercuts would affect 940,000 households and businesses across 36 counties in northern California - hitting an estimated two million people. The outages were expected to last until Monday.
"We have begun implementing the public safety power shutoff", a PG&E official told the media on Saturday evening.
In a statement the previous day, PG&E warned customers that they could be affected by a mass blackout, citing forecasts of potential extreme weather.
The warning came as the company faced scrutiny over its possible role in the fires.
The Kincade Fire in Northern California began seven minutes after a nearby power line was damaged, but PG&E has not yet confirmed if the power glitch started the blaze.
Meanwhile, 90,000 people have been ordered to evacuate towns in northern California due to the Kincade Fire.
The new evacuation order encompasses a huge area of Sonoma County, where the blaze has already burned through 25,455 acres of land.
A state of emergency has been declared in Los Angeles and Sonoma counties, and thousands of firefighters were battling to contain the blazes.
As of Saturday evening, the Kincade Fire was about 10 per cent contained, the BBC said.
The National Weather Service issued a "red flag" warning for areas around the Kincade Fire.
A second massive blaze in suburban Los Angeles termed the Tick Fire had charred 4,615 acres and was 55 per cent contained as of Saturday evening.
All residents who were told to evacuate have returned home.
Firefighters have also been battling several other blazes in the state.
( With inputs from IANS )