On December 8, affecting San Francisco, California, and its environs, over 350,000 customers (buildings) or 940,000 people were affected by an outage caused when the Pacific Gas and Electric Company placed a San Mateo sub-station online at 8:17 am PST, while the station was still grounded following maintenance. This drew so much power from the transmission lines on the San Francisco peninsula that 25 other sub-stations in San Francisco automatically and immediately shut down. Power was not fully restored until almost 4:00 pm PST the same day. Economic costs were estimated in tens of millions of dollars.