ISO-NE Winter 2025/2026 Final Tally: Most Expensive Winter in Wholesale Market History at $6 Billion
The final data is in: ISO New England confirms that the winter of 2025/2026 officially stands as the most expensive winter in the history of its wholesale electricity markets. Battered by the coldest temperatures in 20 years, total energy market values for December, January, and February soared to roughly $6 billion, driving the highest winter peak loads seen since 2018.
Executive Impact — C&I Buyers
- →Index Devastation: C&I buyers floating on index pricing absorbed billions in passed-through fuel costs as the grid relied on dirty backup oil to survive deep-freeze natural gas pipeline congestion.
- →Elevated March Pricing: The hangover continues into Spring. Early March Real-Time LMPs at the Hub averaged $85.68/MWh, far exceeding typical shoulder-season pricing norms.
- →Capacity Market Shift: This severe winter performance will deeply influence upcoming forward capacity auctions as ISO-NE transitions to its new prompt-auction redesign model.
A $6 Billion Winter Reckoning
New England has long struggled with winter reliability due to a heavy reliance on natural gas and constrained pipeline infrastructure. However, the winter of 2025/2026 laid bare the sheer economic cost of these structural limitations. According to ISO-NE and market monitors, the combined energy market value for the core winter months touched an unprecedented $6 billion.
As the region ground through its coldest weather in two decades, heating demand consumed all firm pipeline space. Power generators, forced onto secondary interruptible contracts, found themselves cut off. The grid operator survived by activating Master/Local Control Center Procedure #2 (M/LCC 2) for 18 consecutive days and dispatching massive amounts of expensive fuel oil.
March Spillover and The Spring "Recovery"
The pain hasn't stopped with the arrival of March. Real-time LMPs at the New England Hub averaged $85.68/MWh in the first week of March, with Day-Ahead closing at $73.22/MWh. A localized peak exceeded $170/MWh on the evening of March 2nd due to binding reserve constraints and lingering high fuel prices.
Transmission bottlenecks continue to segment the market. For instance, the Maine Load Zone saw depressed pricing in early March caused by severe, binding constraints on the Maine – New Hampshire Interface, preventing cheaper northern power from flowing down to the heavily populated Boston metro area (NEMA/Boston Load Zone).
Commercial Procurement Takeaways
- Death of the Index Strategy: Index buyers in ISO-NE effectively paid the $6 billion tab. Structuring fixed block forward contracts that completely insulate the winter months (Dec-Feb) is now a mandatory survival tactic for heavy CI industrials.
- Grid Electrification Load: ISO-NE's latest 2026 demand forecast projects sustained, compounding load growth driven almost entirely by the electrification of transit and heating. The grid's peaks are permanently shifting.
Connected Analysis
For an hour-by-hour breakdown of the worst days of the crisis, read our deep-dive into the February 2026 $660/MWh Spikes, or explore how the region plans to restructure the Capacity Market via FERC Filings.
Source: ISO New England Daily Market Watch Reports; RTO Insider; ISO Newswire.