“First thing in the morning, as we opened the door, the calls started pouring in,” said Ms. Maynes, who works in Brisbane, south of San Francisco. “It never stopped ringing.”

While people and companies with means could turn to businesses like Ms. Maynes for backup power, many others did not have that luxury. When they tried to get more information, answers were often not forthcoming.

One option was community resource centers, places run by the utility where affected residents were supposed to be able to cool off and charge their phones. But they often got little information or assistance there because PG&E had not adequately staffed the centers, said a senior state official with knowledge of the situation who was not authorized to speak publicly.

Meanwhile, state agencies, in charge of services like railways and the water supply, were forced to open the state’s emergency operations center, which is normally used for actual disasters like earthquakes and fires, the official said. The center was running at Level 2, the same level it operated on during the Ridgecrest earthquake over the summer. And the local authorities were forced to bear the cost of additional staffing, including overtime hours for police officers, to deal with the shutdown.

This was a big moment for PG&E, which does not have extensive experience using what California officials refer to as a “public safety power shut-off.” Its previous wildfire shut-offs had been limited to tens of thousands of customers — and it was ill prepared for the task.

Ms. Malashenko, deputy executive director for safety and enforcement at the California Public Utilities Commission, arrived at 9 a.m. on Tuesday for the first of her two 12-hour shifts at PG&E’s operations center. She said she was stunned by what she saw. PG&E’s website crashed just ahead of the first rounds of power shut-offs that would leave thousands in the dark.

In addition, the systems the company uses to alert residents and businesses that they would lose power didn’t work as they were supposed to, Mr. Johnson, the chief executive, later acknowledged.