Internal Market Monitor issues winter quarterly report

Despite high costs brought on by unusually cold weather, the power system operated reliably and efficiently during winter 2025/2026, ISO New England’s Internal Market Monitor (IMM) found in its latest quarterly report.

The IMM’s 2026 Winter Quarterly Markets Report, which covers Dec. 1, 2025, through Feb. 28, 2026, presents an assessment of each of the region’s wholesale electricity markets, based on market data, performance criteria, and independent studies.

The winter of 2025/2026 was marked by 19 consecutive days with average temperatures below freezing. The report notes that nearly 45% of the winter’s energy, ancillary services, and uplift costs were incurred during this period, from Jan. 23 to Feb. 10. Although the cold snap was long compared with other recent winters, the report notes that 16 winters since 1950 had longer streaks.

Key findings include:

• The total estimated wholesale market cost of electricity for the winter was $6.53 billion, up 45% from the $4.50 billion reported for winter 2024/2025 and higher than any other winter since 2014.
• Energy market costs totaled $6.08 billion, 51% higher than the previous winter. Day-ahead energy prices, including Forecast Energy Reserve prices, averaged $165.49 per megawatt-hour (MWh). The real-time energy price averaged $137.66/MWh.
• Increased energy costs were driven by natural gas prices, which were up 31% year over year.
• Net imports declined compared to the previous winter as a result of cold conditions and increased demand in neighboring regions. As a result, more of New England’s electricity came from natural gas and oil.