In a statement, NERC blamed “mismatched data” submitted by MISO for a calculation in its 2024 Long-Term Reliability Assessment that resulted in the ERO warning that the region could face energy shortfalls in 2025, while acknowledging its own responsibility for the mistake. 

MISO’s Independent Market Monitor David Patton called out the ERO for what he called a “completely inaccurate” perception at a June 10 Markets Committee meeting of the ISO’s Board of Directors in Minneapolis. (See MISO IMM Blasts NERC Long-term Assessment, Says RTO in Good RA Spot.)  

MISO was the only area of the continent labeled as “high risk” in the LTRA, published Dec. 17, 2024. The designation means that energy shortfalls are likely to occur under normal peak summer or winter conditions in the next five years. NERC said at the time that resource additions had not kept pace with retirements of coal-fired generation since 2023, causing “a sharp [projected] decline in anticipated resources” beginning in summer 2025. (See NERC Warns Challenges ‘Mounting’ in Coming Decade.) 

However, Patton asserted that NERC had incorrectly used MISO’s unforced capacity values instead of its installed capacity, then compared the resulting numbers to an installed capacity requirement. This error, which Patton called “an apples and oranges assessment,” reduced the region’s capacity by more than 10 GW in the LTRA. 

NERC’s statement said the ERO conducted an “in-depth review” and found MISO’s submitted data “overstated the near-term energy shortfall risk.” When the analysis was rerun with corrected data, NERC found MISO should be reclassified as “elevated risk” for the 2025-to-2027 time frame, meaning resources are sufficient for normal conditions but shortfalls could occur under extreme weather conditions.  

“While this data mismatch went unnoticed by MISO and the Midwest Reliability Organization (MRO) that initially collects and vets the data, NERC is ultimately responsible for ensuring the accuracy of its independent reliability assessments,” NERC said. “Going forward, NERC, MRO and MISO are all committed to improving the data validation process to ensure accuracy.”  

NERC said it regrets the discrepancy and plans to post a corrected version of the LTRA “soon,” but it did not specify a time frame. 

MISO’s risk level still could rise to high by 2028, NERC said, “depending on new resource additions [and] retirements.” The new data did not require MISO’s standing in the 2025 Summer Reliability Assessment to be changed, according to the ERO, because that report uses different data. The SRA found that MISO was at elevated risk of shortfalls, along with MRO-SaskPower, MRO-SPP, ERCOT, NPCC and WECC-Mexico in Baja California. (See NERC Warns Summer Shortfalls Possible in Multiple Regions.) 

At the MISO board meeting, Patton said the misleading LTRA already has influenced national policy, as shown by the Department of Energy’s directive to keep a 1.4-GW coal plant in Michigan operating over the summer. (See Consumers Energy Seeking Compensation for Keeping Campbell Open.) He warned the confusion could “lead to FERC ordering market changes that are unnecessary.”