This month, movement in NYISO reference prices was closely tied to capacity markets, which set each zone's Reference Capacity Price (RCP).

New York City's reference price fell 13% year-over-year, to $115/MW-day, as imports over the Champlain Hudson Power Express (CHPE) depressed its capacity price by 21%.

Long Island's reference price rose 30%, to $99/MW-day. Its capacity continued to clear separately from the rest of the state, at a price 72% above last September's. This was due to two changes: NYISO raised Long Island's capacity requirement from 106.5% to 110.3% of peak load, and the 82 MW Pinelawn plant retired.

Upstate and Hudson Valley reference prices rose 2% to 7% from August, even as price volatility fell. This is because Rest of State capacity prices rose 32% after Hydro-Québec sold no capacity into the statewide auction.

Energy arbitrage potential was low, as TB4 spreads, the gap between each day's four priciest and four cheapest hours, hit a 13-month low. Day-Ahead TB4, which sets each zone's Reference Energy Arbitrage Price (REAP), averaged $100/MW-day at the reference node. Real-Time spreads ran below Day-Ahead on most days, but three days in mid-September lifted the monthly Real-Time average 14% above Day-Ahead.

Key takeaways

• New York City's reference price fell 13% year-over-year, to $115/MW-day. Its capacity price of $12.39/kW-month sat 21% below last September, as CHPE has been offering capacity into the city since July.
• Long Island's reference price rose 30% year-over-year, to $99/MW-day. Its capacity surplus halved, to 277 MW, and it cleared at $10.13/kW-month, 70% above Rest of State.
• Upstate and Hudson Valley reference prices rose 2% to 7% from August. Rest of State capacity prices rose 32%, to $5.97/kW-month, as Hydro-Québec's spot auction awards fell from 523 MW to zero.
• Day-Ahead TB4 averaged $100/MW-day, a 13-month low. Real-Time spreads averaged 14% above Day-Ahead, due to three days in mid-September.

Capacity made up 60% to 76% of every zone's reference price

RCP made up 76% of New York City's reference price in September. In every other zone, it made up between 60% and 71%. From May to August, RCP made up 42% to 72% of reference prices.

Year-over-year, reference prices moved downstate and held steady upstate. In New York City and Long Island, RCP moved further than REAP. New York City's RCP fell $16/MW-day, while its REAP fell $1/MW-day. Long Island's RCP rose $27/MW-day, while its REAP fell $4/MW-day.

Upstate, the two largely offset. RCPs rose by $3/MW-day to $4/MW-day, and REAPs fell by $1/MW-day to $6/MW-day.

Hydro-Québec added capacity surplus in New York City and withdrew it upstate

New York City's capacity auction cleared at $12.39/kW-month in September, 21% below last year's $15.73/kW-month. CHPE carries Hydro-Québec power into New York City. It has offered capacity into Zone J since the July auction. Capacity above the city's requirement rose from 629 MW, or 7.7%, last September to 866 MW, or 10.2%. With a larger surplus, the zone clears at a lower price.

Rest of State UCAP, at $5.97/kW-month, was close to last September's $5.89/kW-month. Month-on-month, though, it rose 32% from August. Hydro-Québec cleared 523 MW in the August spot auction and none in September, the same as in September 2025. That explains almost all of the fall in the statewide surplus. It dropped from 2.2 GW to 1.7 GW, or 5.1% above the requirement.