In its 2024-2025 Winter Reliability Assessment, published Jan. 15, SERC Reliability reported that all subregions have enough resources to meet demand under normal conditions this winter. But the regional entity warned that extreme conditions could put the grid under strain and potentially lead to a high risk of energy shortfalls.
SERC produces the WRA each year as a regionally focused companion to NERC’s winter assessment. The ERO published its most recent WRA on Nov. 14, 2024, finding expected demand for most areas to be higher compared to the prior year and warning that multiple regions face elevated risk of energy shortfalls during widespread extreme winter conditions. (See NERC Sees ‘Reasons for Optimism’ as Winter Approaches.)
Like the NERC assessment, SERC’s WRA focused on the three months between December 2024 and February 2025. The RE’s staff collected, verified and validated data on generation and transmission resources, planned outages, and demand projections from entities in its footprint, including balancing authorities, generator owners and operators, planning coordinators, and transmission owners. Data collection began in the first quarter of 2024, with updates incorporated before publication.
The report drew on the National Weather Service’s winter outlook issued in October 2024, which predicted above-normal temperatures and below-normal precipitation across most of SERC’s subregions. SERC noted in the report that, while “the aggregated load forecast total for the SERC region is typically higher in the summer months,” several of its subregions are either dual peaking or winter peaking — namely SERC Central, SERC East, SERC PJM and SERC Southeast.
The vulnerability of these areas to winter conditions was a significant topic in the report, with SERC observing the U.S. suffered 20 separate billion-dollar weather and climate disasters (meaning events in which overall damages reached or exceeded $1 billion) just in the first eight months of 2024. The National Oceanic and Atmospheric Administration since has updated its list, with 27 billion-dollar events confirmed to have occurred in 2024.
Several of these affected SERC’s footprint, including tornado outbreaks in January and April and the Central, Southern and Northeastern winter storm and cold wave in January. The report added that 2024 “was far from the most extreme year for cold weather events on the grid.”
All subregions reported meeting NERC’s recommended reserve margin of at least 15% under SERC’s 50/50 forecast, which represents a load prediction with a 50% chance of being exceeded. However, under the 90/10 forecast, indicating a 10% chance of being exceeded, all but two subregions — SERC Florida and SERC MISO-South — indicated they would fall short of the recommended margins.
The Central, East, Southeast and MISO-Central subregions were assessed as elevated risk, meaning a reserve margin of 6 to 14% for the 90/10 forecast, but the PJM subregion indicated a reserve margin of 4% under those conditions, putting it into the high-risk category. Additionally, SERC noted that all subregions except Florida would be below target reserve margins if load in a 90/10 scenario is underestimated by 10%.
SERC noted several actions that could help with preparations for adverse conditions, including securing fuel inventories and natural gas delivery options. The RE also noted that some SERC entities have oil backups, while others have contracted firm gas storage to guard against supply interruptions.
In addition, SERC said, reliability standards that have come into effect since the winter storms of 2021 and 2022 require generator owners to have winter preparedness plans and annual training, along with other preparations. The RE recommended that entities “pay special attention to their day-ahead load forecasting process” to avoid the kind of forecasting errors that led to the reliability issues associated with those storms.
