A trade group representing multiple MISO power producers has lodged a complaint against retroactive pricing revisions in MISO’s 2025/26 capacity auction, joining Pelican Power in calling the repricing unlawful.

The Coalition of Midwest Power Producers (COMPP) filed the second complaint Dec. 12, asking FERC to “restore confidence” in the capacity auction by ordering MISO to return seized revenues and cease any further resettlements.

Like Louisiana generator Pelican Power’s mid-November complaint, COMPP argued that MISO rolling back capacity payments violates FERC’s filed rate doctrine and rule against retroactive ratemaking. (See Louisiana Gen Co. First to Lodge Complaint Over MISO Auction Error and Price Corrections.)

Pelican Power is a member of COMPP, which COMPP was joined in the complaint by renewable developer JERA Nex Americas and Rainbow Energy Center, owner of the Coal Creek Station in North Dakota.

COMPP told FERC that capacity auction results are financially binding. If MISO’s after-the-fact adjustments rely on too broad an interpretation of MISO’s resettlement authority, “that cannot be squared with the plain language of the tariff or the limitations imposed” by the Federal Power Act.

MISO is making $280 million worth of pricing adjustments to its 2025/26 capacity auction clearing prices, charging an unnamed number of market participants that sold capacity. The RTO announced the repricing after it discovered a yearslong coding error for the loss of load expectation calculation in a third-party vendor’s software. The mistake raised the RTO’s planning reserve margin for almost a decade and caused it to procure more capacity than necessary. (See MISO Discloses $280M Error, Over-procurement in 2025/26 Capacity Auction.)

MISO began issuing the first of three rounds of settlement adjustments in September. The initial set of corrections totaled nearly $77 million. MISO warned market participants that if the adjustment should exceed their credit limit, it would trigger a margin call to cover losses within two business days.

COMPP said MISO should “return hundreds of millions of dollars that have been taken from market participants in connection with MISO’s unlawful resettlement of the 2025/26 Planning Resource Auction” (PRA). It said “any confidence that had been provided by the auction results has been shattered by MISO’s decision to reopen the results months after the PRA concluded and after the 2025/26 planning year commenced on June 1, 2025.”

MISO has said its markdowns or markups aren’t to be construed as it issuing new clearing prices or rerunning or resettling the auction.

But COMPP and companions have countered that MISO effectively is rerunning the market and has significantly reduced the compensation resources receive for capacity.

COMPP said generation owners realize MISO is attempting to correct an error but that MISO can’t replay the auction with different loss of load inputs.

“There simply is no way to predict how changes in the parameters used to run the auction would have changed the behavior of market participants or the resulting [auction clearing prices],” COMPP argued. “The only thing certain is that MISO’s misguided re-run threatens to undermine the confidence in the MISO markets in a manner that does not align with the objectives of encouraging investment or maintaining reliability.”

COMPP requested FERC put an end to MISO “sowing further dysfunction into the PRA.”

According to COMPP, a resource in MISO South would have its $666.50/MW-day summer clearing price set by the 2025/26 PRA reduced by $374.3/MW-day, down approximately 54%. In MISO Midwest, capacity prices are expected to drop by $207.40/MW-day, down 31% from the summertime clearing price.

“The market-wide uncertainty created by MISO’s decision to conduct what amounts to a rerun of the 2025/26 PRA will harm MISO’s ability to retain and attract investment in the baseload resources needed to maintain resource adequacy,” COMPP wrote. The group added that independent power producers stand to be particularly adversely affected. They and their investors will be “incentivized to avoid investments in the MISO markets,” COMPP warned.

MISO: Dismiss Pelican Complaint

MISO responded to Pelican’s complaint Dec. 15, asking FERC to dismiss.

The grid operator said it’s duty-bound by its tariff to correct continuing errors with “appropriate adjustments to address financial impacts.” It said it further has the discretion to make adjustments, and absent a tariff-defined remedy, used its judgment to revise prices using an auction simulation that featured a corrected loss of load expectation value and changed sloped demand curve.

The result, “however harsh, is required by the filed rate doctrine, which requires MISO to follow the tariff and ‘does not yield, no matter how compelling the circumstances,’” MISO wrote.

The RTO argued that suppliers and load-serving entities alike had an expectation that the 2025/26 PRA would be conducted using the correct loss of load expectation calculation, per the tariff.

MISO said the eight-year-old error wasn’t easily detected because it placed “reasonable reliance on the vendor’s representations that the LOLE software was fully compliant” with its tariff requirements.

“Pelican Power, like all market participants, has an understandable pecuniary and partisan interest in the outcome of this case, and as such, the arguments forwarded by Pelican are inherently biased toward the best outcome for Pelican Power and therefore must be viewed with skepticism,” MISO told FERC.