Oct. 24, 2022
Information Only
Adjustment to GMC rates and WEIM administrative fees effective trade date 11/1/22

The continuing changes in weather patterns have increased the demand for energy in California. As a result, the California ISO is experiencing year-to-date over-recovery of the Grid Management Charge (GMC), specifically in the System Operations category. The Nov. 1, 2022 proposed rate decrease will attempt to align the forecasted collected revenue to the budgeted revenue and will minimize the impact of over collections on future rates. Changes to the System Operations rate will also cause the corresponding Western Energy Imbalance Market (WEIM) rate to change. The chart below outlines the GMC category revenue collections forecast for the year.


Budgeted versus Forecast Revenues by GMC Service Category

Service Category

Budgeted Amount





System Operations






Pursuant to Appendix F, Schedule 1, Part B of the ISO Tariff, the ISO will adjust these GMC rate components effective trade date Nov. 1, 2022.


Summary of Proposed Rate Changes

Charge Code

Current Rate

Proposed New Rate


4560 System Operations




4564 WEIM System Operations





The Market Services, Congestion Revenue Rights (CRR) Services, and Reliability Coordinator service charges remain unchanged. The ISO will continue to monitor and assess its revenue collections throughout the year and will make rate adjustment recommendations, up or down, as necessary pursuant to the ISO tariff.


An updated GMC rates sheet with the new rates effective as of the Nov. 1, 2022 trade date is available on the Settlements page of the ISO website.

Please contact your Customer Service representative or ISO Customer Service at 916-608-7320 with any questions.
California Independent System Operator | P.O. Box 639014 | Folsom, CA 95630 | United States
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