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September 22, 2020


Information Only


Adjustment to GMC Rates and EIM Administrative Fees effective Trade Date 10/1/20 


The persistent high temperatures recently experienced in the Western U.S. have impacted the use of energy as businesses and homes respond to the heat wave. The unforeseen increase in energy usage and the increase in certain grid management charge (GMC) rates, which went into effect June 1, 2020, have resulted in the year-to-date over-recovery of the GMC, specifically in the market and system operations service categories.


Based on data through August 2020, the current California ISO revenue collections forecasted for the year show that the GMC for the Market and System Operations services categories will differ by more than the greater of 2% or $1 million. Accordingly, the ISO Tariff requires that the associated GMC rates be adjusted along with the corresponding Western Energy Imbalance Market (EIM) Administrative Fees.


The ISO has decided, effective on trade date Oct. 1, 2020, to revert back to the rates for the Market and System Operations services categories that were in effect at the beginning of the year. The October 1 rate adjustment will attempt to align the forecasted actual revenue to the budgeted revenue. The corresponding EIM Administrative Fees will also be reverted back to the rates that were in effect at the beginning of the year. The chart below outlines the GMC Category revenue collections forecast for the year.


Budgeted versus Forecast Revenues by GMC Service Category

Service Category

Net Budgeted Amount

Revenue Forecast



Market Services





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 Oct. 1, 2020.


Summary of Proposed Rate Changes

Charge Code

Current Rate

Proposed New Rate


4560 Market Services




4561 System Operations




4564 EIM Market Services




4564 EIM System Operations





The reliability coordinator service charge remains unchanged. The ISO will continually monitor and assess its revenue collections and will make recommendations of any rate adjustments, up or down, if necessary.


The ISO has posted a schedule showing the rates effective for the Oct. 1, 2020 trade date on its website at


Contact your Customer Service representative or call ISO Customer Service at 916-608-7320.
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California Independent System Operator | P.O. Box 639014 | Folsom, CA 95630 | United States