Power grid strained by heat, nearly 7,000 PG&E customers lose power in San Francisco

SAN FRANCISCO - Nearly 7,000 Pacific Gas & Electric customers in San Francisco lost power Thursday afternoon, as a historic heat wave has stifled the Bay Area since the Labor Day holiday weekend. 

By 4 p.m., the majority of customers' who lost power in San Francisco had their energy restored. But the heat has certainly tested the state's power grid. 

PG&E's outage map reported 6,496 (down from 6,922 minutes earlier) customers were affected by the unplanned outage as of 3:27 p.m. There were no planned Public Safety Power Outages for the area, the utility said. The afternoon outage swelled from 5,826 who were without power closer to 3 p.m.

This week's oppressive heat relatively abated on Wednesday after record temperatures on Tuesday. But on Thursday, the mercury once again rose as was forecast. 

PG&E did not confirm the source of the outage in San Francisco. There was no estimated time of full restoration. 

In previous days of consecutive widespread Bay Area outages, the utility had reported only one or two customers in the city without power, with the largest concentration of outages in the South and East Bay. 

SEE ALSO: California power outages: what you need to know

California ISO has called for another flex alert from 3 p.m to 10 p.m., warning consumers to conserve energy after daily threats of rotating power outages. Those outages from strain to the power grid were avoided due to conservation efforts. However, some utilities in the Bay Area, like in Palo Alto and Alameda, did see the power go out as a result of rotating outages. 

Cal ISO expects power usage to decrease on Friday. PG&E and the California Department of Water Resources are co-sponsoring a sizable array of emergency generators at an electric substation in Cloverdale. 

A spokesperson said the 13 generators has the capability of bringing on 16 megawatts into the grid. 

You can check the PG&E current outage map here.