ISO-NE wind generation ran 68% above year-ago levels through September 2026, driven by new offshore capacity

Monthly wind generation in ISO New England averaged 68% higher in the first nine months of 2026 compared with the same period in 2025, according to data published by the U.S. Energy Information Administration on 14 October 2026, drawn from the agency's Hourly Electric Grid Monitor^[1]. The jump is the most visible statistical signal yet that two large offshore projects - Vineyard Wind 1 and Revolution Wind - are materially reshaping the region's generation mix.

What drove the increase

The proximate cause is new offshore capacity coming online. Vineyard Wind 1, an 800 MW project off the Massachusetts coast, completed turbine installation and reached full construction in March 2026, having first delivered power to the ISO-NE grid in January 2024. Revolution Wind, a 704 MW project contracted to Rhode Island and Connecticut, delivered first power on 13 March 2026 and installed its 65th and final turbine in September 2026, with full-capacity output expected before year-end.

Together the two projects represent the largest single-year addition of wind capacity in ISO-NE's history. ISO-NE's 2025 Annual Markets Report had flagged both as near-term supply additions with the potential to "make a meaningful contribution" toward meeting anticipated demand growth.

The offshore additions sit on top of an existing onshore fleet. Wind accounted for roughly 4.1% of ISO-NE's net energy for load in 2025, with about 2,500 MW of installed capacity in the region at that point. The new offshore projects more than double the effective wind nameplate available to the grid.

Caveats in the data

The 68% figure is a year-on-year average across nine months, not a measure of sustained output. Vineyard Wind has faced operational headaches: as of August 2026, 36 of its 62 turbines were reported to be idle amid an ongoing dispute over turbine blade repairs, with output falling below levels needed to meet financing obligations. That drag means the 68% uplift likely understates what the fleet could deliver at full availability.

Revolution Wind's ramp has been smoother but opaque. Ørsted reported in May that the project was approximately 94% complete and generation was continuing to ramp up, but granular output data have not been made public.

On the upside, ISO-NE recorded its highest-ever instantaneous offshore wind output on the evening of 30 August 2026, when the region's three offshore wind plants combined to send 930 MW to the grid.

What the grid operator is watching

ISO-NE has consistently flagged offshore wind as particularly valuable in winter, when output tends to be highest and pipeline-constrained gas supply is tightest. The grid operator noted in December 2025 that both Vineyard Wind and Revolution Wind "are particularly important to system reliability in the winter when offshore wind output is highest and other forms of fuel supply are constrained."

The interconnection queue points to further growth. Wind accounts for about 44% of the projects under interconnection study in ISO-NE as of January 2026, representing over 6,100 MW of proposed new capacity. A transitional cluster study covering 26 projects - including the 1,200 MW SouthCoast Wind 1 - was launched in 2025 under a new review framework, with the first full cluster study request window opening in October 2026.

The key variable heading into winter is Vineyard Wind's turbine repair timeline. If blade replacements proceed and the project approaches its 800 MW nameplate, the year-on-year wind generation gap will widen further. If repairs stall, the 68% headline figure may flatter the underlying picture. ISO-NE's winter adequacy assessment, expected in the coming weeks, will be the next data point to watch.