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Plant Performance Monitoring

The Electric Generation Performance Branch (EGPB) monitors and analyzes performance data of power plants in an effort to ensure that generating facilities are appropriately maintained and operated, and that electrical service to the customers is reliable and adequate.  EGPB staff looks at both real-time and historical plant data.



Real-Time Data

EGPB staff receives real-time information on power plant outage through a database from the California Independent System Operator (CAISO) and daily reports from Generating Asset Owners (GAO). 


CAISO is a non-profit public organization in charge of a majority of California’s high-voltage wholesale power grid operation.  It serves as a link between power plants and utility companies in balancing the supply and demand of electricity in the State.  CAISO has a database called Scheduling Logging for the ISO of California (SLIC), which collects transmission and generation outage information submitted by power plants and/or utility companies.  EGPB staff can access SLIC to obtain real-time or historic information on power plant outage throughout the State.


EGPB also receives daily status reports from GAO for thermal plants greater than 50 megawatts (MW).  GAO provides status on each operational unit by 9:00 am, every weekday.  An EGPB staff compiles and records all unit status information.  If a unit is out of service or curtailed by more than 50 MW, an EGPB engineer will contact the power plant for more outage information and may arrange for an on-site inspection.

Historical Data

EGPB staff collects, compiles, and analyzes historical performance data on jurisdictional power plants.  The three main data sources come from the North American Electric Reliability Corporation (NERC) Generating Availability Data System (GADS), SLIC, and information gathered during an outage inspection. 


NERC GADS is a group of databases used to collect, record, and retrieve operating information from power plants in North America.  The data is used to improve performance of electric generating equipment; and to support equipment reliability and availability analysis by GADS data users. EGPB staff can access GADS to perform performance analysis on jurisdictional power plants, reconcile information between GADS with other sources such as SLIC, and monitor timely and accurate data submittal to NERC.


Per General Order (GO) 167, Sections 10.3.2 to 10.3.4, all jurisdictional generators must submit design, event and performance data to the NERC GADS database.  Jurisdictional generators must sign a release form, permitting NERC to share the GADS data with the CPUC.


If you have questions about the Plant Performance Monitoring program, please either call (415) 355-5503 or email


Last Modified: 1/27/2012

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