​New York City's reference price reached $244/MW-day in May 2026, up 105% year-over-year. 94% of that increase came from the reference price’s capacity component. NYC's unforced capacity (UCAP) price more than doubled from a year earlier, to $32.59/kW-month. A mid-May heat wave also added a lift through wider top-bottom spreads.

The capacity surge pulled NYC far ahead of upstate zones, where reference prices ran $77-84/MW-day. For a New York City battery, the ISC reference price is overwhelmingly driven by the capacity price, and this month it doubled.

Key takeaways

• NYC's reference price hit $244/MW-day, up 105% year-over-year. Capacity prices drove roughly 94% of the gain as NYC's UCAP price more than doubled year-over-year to $32.59/kW-month.
• Real-time TB4 spreads averaged $302/MW-day, up 132% year-over-year. A May 17-20 heat wave drove the month's volatility, lifting day-ahead and real-time spreads across every NYISO zone and elevating the Reference Energy Arbitrage Price (REAP).
• NYCA regulation peaked at $51/MWh on May 17 as the temperature ramped up. This is untracked upside, revenue beyond the Reference Capacity Price (RCP) and REAP that batteries capture by following the regulation signal through the highest-priced hours.

New York City doubled its capacity price year-over-year

New York City is transmission-constrained and therefore NYISO requires a minimum share of the state’s capacity to sit inside the city. When bid NYC capacity is tight, the NYC capacity market clears far higher than the unconstrained rest of the state.

With the summer Capability Period starting May 1, NYC UCAP cleared at $33/kW-month, more than double May 2025's $15/kW-month and five times April's winter-period $6/kW-month. Long Island cleared at $11/kW-month and the rest of the state at $8/kW-month.

New York City did get a major new import line mid-month: the 1,250 MW Champlain Hudson Power Express began operating on May 13. But it missed NYISO's notice deadline, so it did not count as capacity in May, and only becomes eligible to offer from the July auction.

The capacity price flows straight into the RCP. NYC's RCP reached $212/MW-day, up from about $95/MW-day a year earlier, under NYISO's new 2026-27 accreditation factors. Those factors exclude CHPE as well, computed as if the line were not there.

For a New York City battery, capacity alone currently exceeds the entire reference price of any upstate zone.

Day-ahead and real-time spreads rose across every zone

TB4 spreads widened across New York year-over-year, in both the day-ahead and the real-time markets. At the reference node, real-time TB4 averaged $302/MW-day in May 2026, up 132% from $130/MW-day a year earlier. Day-ahead TBs averaged $131/MW-day.

REAP is defined by the day-ahead spread, so the day-ahead market sets the energy component of the reference price.

Long Island led day-ahead TBs at $164/MW-day. New York City followed at $128/MW-day. The upstate zones clustered lower, with West weakest at $97/MW-day. Long Island therefore carried the highest REAP in the state.

The same order held in real-time, at higher levels. Long Island led at $285/MW-day, up 36% year-over-year. New York City followed at $203/MW-day, up 45%. Real-time spreads beat day-ahead in every zone.

That gap is upside the reference price never credits, and batteries that trade the intraday swings can outperform the REAP.

A mid-May heat wave drove the month's volatility

A mid-May heat wave sent New York prices sharply higher. New York City reached 93°F on May 19, and statewide highs peaked at 88°F on May 18, roughly 21°F above the May 2025 average.

Real-time prices spiked to $305/MWh on May 17 as load climbed, the single sharpest moment of the month.

Across the month, real-time prices ran above May 2025, with sharper evening peaks. The monthly real-time mean reached $35/MWh, up from $32/MWh a year earlier. Prices swung the other way on Memorial Day weekend, falling to -$21/MWh on May 24 as light holiday load met strong wind and the solar ramp.

The heat wave also lifted ancillary service prices

The same heat that widened energy spreads lifted ancillary service prices. Regulation moved first. NYCA regulation cleared $51/MWh on May 17, more than triple its $14/MWh median for the month.

Reserves followed a day later. On May 18, all three reserve products jumped above $20/MWh from a near-zero baseline: 10-minute spinning at $22, 10-minute non-synchronous at $22, and 30-minute at $20.

Ancillary services sit outside the reference price, which credits only capacity and the day-ahead energy spread. The ISC settles a battery against that reference, so regulation and reserve revenue counts toward earning beyond the strike price.

What does May tell us?

New York City's capacity price doubled year-over-year, and its reference price now sits more than three times upstate's. The summer reset reopens this gap every year, but 2026 widened it far more than 2025.

For most of the state, the reference price is still tied to capacity clearing prices. Energy arbitrage and regulation, lifted by the mid-May heat, are where batteries can outperform it.

For more on how the ISC works, what drives the Reference Price, and how batteries can outperform it, read Modo Energy's ISC explainer here.