Key Insights from NYISO's Winter Reliability Assessment
As New Yorkers brace for another winter, the New York Independent System Operator (NYISO) has released its 2025 Winter Reliability Assessment – a critical snapshot of how the state’s electric grid is expected to perform during the coldest months of the year. This document is a roadmap for reliability and resilience in an era of rapid energy transition.
NYISO is the nonprofit organization responsible for managing New York’s electric grid and wholesale markets. Every year, we evaluate the grid’s ability to meet winter demand, factoring in weather extremes, fuel availability, generator performance, and evolving energy policies.
Aaron Markham, Vice President of Operations, delivers the assessment before market participants and stakeholders, which includes state and federal regulators, environmental and consumer advocates, generators, and utilities.
Winter reliability is especially important in New York, where frigid temperatures can drive up heating demand and strain the grid. The 2025 assessment reflects a complex balancing act: maintaining reliability with an aging fossil fuel fleet and more intermittent renewable resources.
Issues associated with maintaining grid reliability during the winter months are expected to become more acute in the coming years. As Winter Storm Elliott demonstrated, the connection between fuel security and grid reliability is an important topic that requires more attention and discussion. Priority is given to firm customers on the natural gas system. The North American Electric Reliability Corporation recently raised concerns about fuel security during extreme winter weather events and called for increased coordination among all stakeholders to maintain reliability.
Key Findings from the 2025 Winter Reliability Assessment
- Peak Demand Forecast: NYISO anticipates a winter peak demand of 23,291 MW, with 28,900 MW of “firm” capability available to meet winter loads.
- Extreme Weather Scenarios: Under severe cold conditions, however, demand could spike to ~25,000 MW. NYISO has modeled these scenarios to ensure the grid can respond because such weather is increasingly common, as evidenced in recent winters.
- Fuel Supply Risks: Natural gas availability remains a concern during prolonged cold snaps. Dual-fuel generators (those that can switch to oil) are critical for backup. (For health and safety reasons, natural gas is prioritized for residential consumers to heat their homes in the winter.) Certain generators can switch to oil as a backup fuel when gas demand is high or gas is unavailable to generators.
- Retirements and Renewables: Several fossil fuel plants are slated for retirement, while wind and solar capacity continue to grow. However, winter output from renewables is variable, and intermittent, requiring careful planning with the need for backup resources to serve consumer demand and maintain reliability.
- Transmission Constraints: Bottlenecks in certain regions, especially downstate, could limit the movement of power during peak periods. NYISO is working with stakeholders to address these vulnerabilities.