New England's power system operated reliably through the winter of 2024/2025, despite it being the first winter in a decade with colder-than-normal temperatures. There were two notable cold snaps, short in duration, from Dec. 22 to 23 and Jan. 20 to 22.
The New England generation fleet and transmission system performed well overall, and ISO system operators did not need to take any emergency actions to maintain system reliability. The cold weather led to higher prices in the region's wholesale electricity markets due to higher fuel prices and increased consumer demand for electricity.
Colder-than-normal temperatures
Winter 2024/2025 was the first since 2014 to see below-normal temperatures over the course of an entire season. The average temperature was 0.6°F below normal, with each month coming in below average: 0.1°F, 0.8°F, and 1.1°F below normal in December, January, and February, respectively. Jan. 22 was the single coldest day of the season, with a daily average temperature of 8.8°F.
Precipitation and snowfall totals were also below normal this winter. Snowfall recorded in Boston was 8.7 inches less than normal, while Hartford saw 16.5 inches less snowfall than normal.
Increased consumer demand for electricity
Consumer demand peaked this winter at 19,607 megawatts (MW) on Jan. 22, slightly below projections entering the season.
Average demand was up compared to last winter. Most notably, February saw an average system demand of about 14,508 MW, up 1,350 MW from last year and the highest February value since 2015. December and January averages were the highest since 2017 and 2018.
Wholesale electricity prices, costs rise
Average natural gas prices in December 2024 were 184% higher than the previous year. January and February prices rose by 120% and 319%, respectively. Natural gas is the predominant energy fuel in New England, and the rise in prices aligns with the demand associated with colder-than-normal temperatures seen this winter. These higher fuel prices, coupled with increased consumer demand, led to higher market costs in the region compared to recent years. The wholesale energy market was valued at $4 billion in the winter of 2024/2025, the second highest value since 2013/2014, and up from last year's $1.6 billion.
Resource mix
Natural gas and nuclear power generated the majority of grid electricity consumed in New England this winter, accounting for approximately 49% and 28% of the supply mix, respectively.
Colder temperatures led to an increase in electric heating demand and increased demand on the natural gas heating system, leading to higher natural gas prices. As a result, coal and oil become more economical to run than natural gas during times of tight system conditions, resulting in higher emissions.
Coal- and oil-fired generation accounted for just under 4% of all electricity produced in New England an increase from last winter, when they accounted for less than 1%.
Hydroelectric resources accounted for approximately 7% of the region's generation, down from 10% last winter. Other renewables, including landfill gas, methane, refuse, and wood, generated approximately 5% of electricity this winter.
New England received net imports of 6,672 gigawatt-hours (GWh) of electricity from neighboring regions from December through February, up from 5,366 GWh the previous winter.
Estimated emissions
The mix of resources used to produce the region's electricity is a key driver of carbon dioxide (CO2) emissions. ISO-NE estimates these emissions through an analysis that blends data on electricity generation by fuel type with an emissions factor for each fuel that is based on data from the Environmental Protection Agency.1
From December through February, CO2 emissions from New England power plants were up about 8% from the previous winter, rising from an estimated 7.1 million metric tons to about 7.7 million metric tons. This increase can be attributed to the temperature during this period as weather is a significant driver of load in the region. The New England states experienced cooler temperatures and more heating degree days on average in winter 2024/2025 than in winter 2023/2024.
A decrease in generation from natural gas plants meant a 4% decrease in emissions from these resources. At an estimated 5.2 million metric tons of CO2, they accounted for 65% of the regional total. Oil- and coal-fired generators produced about 892,802 metric tons of CO2 this winter, nearly eight times last winter's total of 115,427 metric tons. These resources accounted for 11.6% of the total. CO2 emissions from refuse, wood, landfill gas, and methane rose 1%. At an estimated 1.8 million metric tons, they accounted for 24% of the region's total.
