July 18, 2022
Information Only
Adjustment to GMC rates and WEIM administrative fees effective trade date 8/1/22

The recent economic upturn and 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 Market Service category. The August 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 Market Service 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





Market Services






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


Summary of Proposed Rate Changes

Charge Code

Current Rate

Proposed New Rate


4560 Market Services




4564 WEIM Market Services





The Systems Operations, 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 Aug. 1, 2022 trade date is available on the Settlements page of the ISO website.

Contact your Customer Service representative or call 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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