​ISO-NE energy prices rose year on year in May 2026, with the gains concentrated in the evening peak. Internal Hub real-time prices averaged $49/MWh, up from $33 in May 2025. Day-ahead prices averaged $46/MWh, up from $35.

Battery arbitrage value rose alongside prices. Four-hour top-bottom (TB) spreads at the Internal Hub averaged $214/MW-day in real time, 85% above the prior May. The story of the month is a tighter evening market and a wider gap between midday and evening prices.

Load stayed mild most of the month, averaging 10.8 GW, but a warm spell over May 18 to 20 pushed demand to a monthly peak of 18.9 GW. That surge briefly tightened the system and drove the month's highest prices.

Key takeaways

• Real-time prices at the Internal Hub averaged $49/MWh, up from $33 a year earlier. Day-ahead prices averaged $46/MWh.
• Gains concentrated in the evening, not across the board. Real-time prices averaged $40/MWh at midday and $67 by 7 PM, widening the intraday range batteries capture.
• Four-hour real-time TB spreads averaged $214/MW-day, up 85% year on year. May spreads are more in line with April's $177 but below January's weather-driven $491 winter peak.
• Maine had the widest four-hour real-time spreads at $263/MW-day, and Connecticut had the narrowest at $204. Maine also had the lowest average energy prices.
• Nuclear generation returned from refueling and wind generation rose 70% compared to 2025 as offshore capacity came online, with wind at a 103% capture rate.

Real-time prices averaged $49/MWh, with the gains in the evening peak

Internal Hub real-time prices averaged $49/MWh in May 2026, up from $33 in May 2025. Day-ahead prices averaged $46/MWh, up from $35.

The rise was not a broad, all-hours lift. Hourly real-time prices held at $40/MWh at midday, then peaked at $67/MWh at 7 PM, as solar fell off and demand built into the evening. Average peak load rose only 4% to 13.6 GW. The gains reflect evening tightness rather than load growth, and the widening intraday range is what fed the bigger spreads.