February 25, 2024
ICC Staff Demurs on Decision over Ameren’s MISO Membership
Commission Staff Wrap Up NOI Without Action
An Ameren Illinois substation expansion in 2021
An Ameren Illinois substation expansion in 2021 | Ameren Illinois
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Illinois Commerce Commission staff have passed on recommending that Ameren and two smaller Zone 4 utilities depart MISO for PJM.

Illinois Commerce Commission staff have passed on recommending that Ameren and two smaller Zone 4 utilities depart MISO for PJM

ICC staff issued a final report Jan. 25 on the notice of inquiry they opened last year after the ICC directed Ameren to study the cost-benefits of leaving MISO and joining PJM. Ameren commissioned Charles River Associates, which found it would cost southern Illinois customers about $3.4 billion from 2025 to 2034 for Ameren to disentangle itself from MISO and join PJM. The study considered energy trade benefits, transmission expansion to tap into PJM, RTO costs and exit and entry fees to switch grid operators.

In comments on the study last year, ICC staff said PJM’s true capacity market style could be a better match for Ameren than MISO’s residual capacity auctions. They also said that a continued home in MISO could be fraught with resource adequacy risks when compared to PJM because MISO is poised to add more solar power and energy storage. (See ICC Staff: More to Consider in Possible Ameren Illinois Exit from MISO.) 

Ultimately, ICC staff said that although they combed through comments on how the study methodology and inputs could be tweaked to show greater future benefits of PJM membership, “it is not clear that implementing such changes would change the conclusion from the Ameren report that Zone 4 joining PJM would result in incremental net costs for [Ameren], ComEd and the State of Illinois overall.”

Staff said they weren’t recommending the commission “take any specific action” to change Ameren’s — and possibly by extension, City Water Light and Power and Southern Illinois Power Cooperative’s — RTO membership.

However, staff added it might be worthwhile for the commission to re-evaluate Ameren’s status as a MISO member in the future. 

“ICC staff notes that the information submitted in this proceeding suggests that assessing the net benefits of [Ameren’s] MISO membership is not a static assessment and will change over time. As a consequence, ICC staff further recommends the commission leave open the possibility of further analyses should future circumstances warrant them,” they wrote.

Capacity MarketGenerationIllinoisMISOPublic Policy

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