May 27, 2022
 Information Only
Legal & Regulatory
Short-Long Start Unit Resource Tariff Definition Updates: Effective Date 6/1/22

The California ISO is updating the definitions for Short and Long Start unit resources in the ISO Tariff and Business Practice Manuals (BPMs), effective June 1, 2022.


With regards to how Short and Long Start resources are defined, the Medium Start definition will be removed and rolled into the Short Start definition. The term “start” references the amount of cycle time a resource requires to move from an offline to an online status and reach its minimum load production. The cycle time for Short Start resources to be considered for both Day-Ahead and Real-Time unit commitment, and for Bid Cost Recovery (BCR), has been updated to 255 minutes or less.


These simplifications are intended to clarify operational and settlement communications and outcomes for the Western Energy Imbalance Market (WEIM) and the ISO market participants.


Impacted Business Practice Manuals include:


Additional information on these new definitions is available using any of the following links:


Please contact Customer Readiness at with any questions.

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