An emergency called by CAISO may cause power to be cut in 2 possible ways:
- Power cuts by the block system, which is a methodical approach, or,
- Power cuts at random triggered in a short-notice emergency (extremely rare).
CAISO monitors the California electric grid to ensure there's enough electricity available for use. If the used electricity increases to the point where there is not enough "spare" reserves (i.e. usage vs. demand), CAISO will place a request to all California utilities to turn off power (i.e. "shed load"), to reduce the amount of energy being used.
PG&E has established with CAISO and the CPUC a methodical approach to reducing load in these situations. This approach uses a block system, to ensure critical public services (i.e. hospitals, fire stations, etc.) are not affected. The block system is also used to allow PG&E to cut power to different blocks on a rotating schedule, so that the same customers are not repeatedly affected by power outages caused by a stage 3 emergency.
The need for outages is determined by the statewide grid operator and not PG&E. Rotating outages are not related to any issues with PG&E’s equipment or its ability to deliver energy locally.
Visit Help Prevent Rotating Outages for more information.
You can also visit the California ISO website for additional information.