Stakeholder voices criticizing the design of MISO’s proposed, probabilistic capacity accreditation outnumbered those expressing support before FERC.  

MISO filed with FERC for a new, direct loss-of-load accreditation style in late March. The RTO wants to move to a capacity accreditation for all resources that blends resources’ historical availability with projected performance during simulated loss-of-load events (ER24-1638). (See MISO: New Capacity Accreditation Filing Imminent.) Stakeholders’ reactions to the filing rolled in this week.  

MidAmerican Energy protested MISO’s filing, saying the marginal accreditation style would lower dispatchable resources’ values across its fleet with little explanation and result in undue discrimination to renewable energy. The company said examples MISO provided earlier to stakeholders to illustrate capacity values showed “accreditation values were well below the resource’s actual performance.” 

“Compounding this issue, MidAmerican has been unable to recreate … MISO’s results or get information from …MISO that explains why MISO’s results are vastly different from actual operations,” it wrote to FERC.  

Consumers Energy likewise said MISO’s accreditation proposal suffers from a lack of data transparency around class averages. It said it was impossible to understand why MISO set a pumped storage class average of 98% in the summer and fall seasons but just 50% in winter and 67% in spring for a consistently dispatchable resource.  

MISO’s accreditation would use a two-step process. First, MISO would calculate a probabilistic, resource-class average accreditation using its loss-of-load expectation analysis. MISO then plans to tailor resource class-level accreditations to individual generators based on their availability during both normal operating conditions and high-risk hours, including hours with low margins or emergency events in place. MISO plans to give greater weight to hours that contain emergency or near-emergency conditions in the ensuing accreditation.  

Most resources’ credits would shrink under the new accreditation. Resources would be divided by fuel type: gas, coal, combined-cycle hydro, nuclear, energy storage, pumped storage, run-of-river, biomass, wind and solar. 

A joint protest from Sierra Club, Natural Resources Defense Council, Sustainable FERC Project, Fresh Energy and Clean Wisconsin argued that because MISO’s loss-of-load expectation analysis features heavily in its accreditation and would have “outsized” impacts, MISO should have included its loss-of-load study methodology for scrutiny in its filing. 

A group of seven transmission-dependent Midwestern utilities criticized MISO’s accreditation design for relying on its self-described imperfect loss-of-load expectation analysis and inappropriately grouping dual-fuel combustion turbines into the same resource class as single-fuel counterparts. They called the design “not yet ready for prime time” and asked FERC to reject it.  

The MISO Cities and Communities Coalition — a collection of local governments within MISO focused on decarbonization including Minneapolis, New Orleans, St. Louis and Des Moines — said it worried MISO’s probabilistic accreditation would stymie clean energy targets. The coalition said MISO hasn’t provided enough detail around how it will treat energy storage in modeling and dispatch for accreditation purposes. It also said it worried the accreditation devalues solar generation’s contribution by not recognizing solar would subdue an afternoon peak and send it later into the evening, thus reducing reserve requirements on all resources.  

Entergy and Cleco also argued that elements are missing from MISO’s proposal, including how MISO would distribute planned outages across resource classes in probabilistic modeling, how MISO would factor resource deliverability into accreditation and how MISO would model deployment of energy storage resources. The two said FERC should order MISO to make another filing to fill in those blanks.  

Alliant Energy said while it “understands the need for changes to MISO’s markets in the face of the evolving resource mix,” it asked FERC to be open to delaying MISO’s rollout beyond the 2028/29 planning year.  

Clean energy proponents — Advanced Energy United, the American Clean Power Association, Clean Grid Alliance, Invenergy, NextEra Energy Resources, the Solar Energy Industries Association and the Southern Renewable Energy Association — jointly asked FERC to reject the filing. They argued MISO’s accreditation proposal would “unrealistically undervalue certain resources below their actual and likely contributions to system needs.” They also said MISO’s filing lacks detail and argued the set of resource classes aren’t nuanced enough and omit “technological and geographical distinctions” that lower capacity contributions. 

On the other hand, DTE Energy said MISO’s accreditation is a “resource-agnostic approach that appropriately shifts resource accreditation to focus on time periods of greatest reliability risk.” Constellation Energy also said MISO’s approach would help address operating challenges wrought by an evolving resource mix, extreme weather and load growth.  

The Michigan Public Service Commission said it supported MISO’s move to a probabilistic accreditation, calling it a “culmination of historical incremental changes, along with rapidly changing conditions in recent years such as continuing resource transitions, rise in extreme weather events, shifting load patterns and the reduction of reserve margins.” The commission said the accreditation is an honest attempt to “address the growing misalignment of the current system, which fails to properly represent risk, and the reliability of resources in the context of newly developing risks.”  

The Organization of MISO States itself was more cautious with its backing. It said while it “broadly” supported the accreditation, it emphasized MISO’s three-year transition period is essential, particularly in understanding how the direct loss-of-load approach would affect not only accreditation, but how MISO would divvy up reserve margin requirements among load-serving entities (LSEs).  

MISO is set to apply its probabilistic model not only to resources participating in its capacity auctions but extend it to its calculation of planning reserve margin requirement, which it divides into responsibilities among load-serving entities.  

However, MISO’s filing did not detail how it would use the probabilistic model to allocate its planning reserve margin requirement among LSEs, leaving that to a later, separate filing. Today, MISO metes out the requirement on a load-ratio share.  

“Given the significant changes the (direct loss-of-load) methodology could impose on the resource planning efforts by LSEs and their respective retail regulators, and given the need for further discussions around modeling improvements, MISO’s proposed three-year transition period is an essential component of MISO’s filing,” OMS wrote. It asked that MISO publish semi-annual status reports on how the probabilistic model would influence reserve requirements so LSEs can make better generation investment decisions.  

Arkansas Electric Cooperative Corp. also expressed concern the new accreditation would introduce “dramatic changes to the capacity allocation process and increased financial burden for a significant number of LSEs.”