The region’s annual electricity consumption will increase by about 9% over the next decade, ISO New England projects in its 2026-2035 Forecast Report of Capacity, Energy, Loads, and Transmission (CELT).
Slightly lower than last year’s edition, the energy forecast reflects more conservative assumptions around future adoption of electric vehicles and heat pumps in light of government policy changes, it said on May 1.
Every year, load forecasters at ISO-NE examine past electricity use, historical weather patterns, expected economic growth, state-level carbon reduction goals, and other factors to develop the long-term projections at the heart of the report.
Data published in the report are a foundational resource for the ISO’s system planning and reliability studies.
In addition to forecast data, the CELT Report provides detail on New England’s energy resource fleet, including:
• The potential output of resources participating in the capacity market
• The total generating capability of resources in the region
• A breakdown of the region’s generators by fuel/unit classification
Usage trend reversing
New England’s net annual energy use has trended downward since 2005, mainly due to more efficient heating and cooling systems, appliances, and lighting, as well as the increased prevalence of behind-the-meter photovoltaics (BTM PV) generation. ISO-NE predicts that trend will reverse over the next decade. Steady growth in net annual energy use is expected as state policy goals for carbon emissions reductions continue to incentivize electrification of heating systems and transportation in the region.
This year’s forecast builds on techniques developed during the 2025 CELT Report cycle that allow ISO-NE to model future demand on an hourly basis. This approach treats evolving patterns of energy production and consumption with greater precision than earlier forecasts, which focused primarily on annual energy and seasonal peak projections.
For the 2026 CELT Report, the long-range forecast is made up of six components:
The base forecast (1) models typical electricity use in homes and businesses. For several years, ISO-NE forecasters have been tracking rising demand from electric vehicles (2) and electrified heating systems (3), as well as demand reductions associated with BTM PV (4). This year the ISO incorporated two additional forecasts into the CELT Report.
The large load forecast (5) models major new users of electricity that could include data centers, crypto mining facilities, and industrial agriculture. Prospective large loads in New England remain limited in number and scale.
However, large loads are presenting challenges for electric grids in other parts of the country. ISO-NE is proactively developing methods to analyze large loads to be prepared for possible future growth in this area. The final forecast component (6) assesses growth in battery energy storage systems (BESS) co-located with behind-the-meter solar. These battery systems increase demand for grid electricity when charging and decrease demand when discharging. BTM BESS is expected to have a relatively small impact on overall demand over the forecast horizon.
The ISO combines all six forecast components to create a long-range projection that models electricity demand in each hour of the day — for many years into the future. The 2026 CELT Report focuses on forecasted annual energy use and seasonal peak demand over the next 10 years.
Net annual energy use is expected to grow by 0.9% annually over the 10-year period.
BTM PV is projected to reduce consumption of grid electricity by 7,056 gigawatt-hours (GWh) this year, rising to 10,179 GWh in 2035. In other words, without BTM PV, annual energy use would be about 6% higher in 2026 and 8% higher in 2035.
Electric vehicles are expected to increase energy use by 7,074 GWh in 2035, while heating electrification increases use by 7,165 GWh that year.
Seasonal peaks converge
Peak demand is a measure of the highest amount of electricity used in a single hour. The CELT Report includes forecasts for both summer and winter peaks.
ISO New England analysts use extensive climate-adjusted weather data to derive typical peak conditions reflected by the 50/50 forecast, which corresponds to a 50% chance that peak demand will be above or below the forecast.
Traditionally, the expected annual peak in New England occurs during the summer. But by 2035, the ISO predicts the winter 50/50 net peak will nearly match the summer 50/50 net peak as the electrification of heating accelerates.
The 90/10 forecast — which reflects hotter, more humid peak conditions in the summer and colder temperatures in the winter — means there is a 10% chance that peak demand will be higher than the forecast.
Under typical summer weather conditions, net peak demand is expected to rise at an annual rate of 0.6%. For hotter weather, the net peak is expected to rise by 0.7% annually.
BTM PV reduces the summer peak by an average of 1,936 megawatts (MW) in each year of the 10-year forecast. Although in past years the summer peak typically occurred in the afternoon, widespread adoption of BTM PV has effectively pushed the peak toward sunset. This means that even as more BTM PV comes on line, its impact on summer peaks will not significantly increase.
Transportation electrification is expected to contribute 594 MW to 50/50 summer peak demand in 2035.
Under typical winter conditions, net peak demand is expected to rise by an average of 2.6% annually through the winter of 2035/2036. For colder weather, the net peak is expected to increase by 2.9% annually.
Heating electrification is projected to contribute 5,533 MW to the 50/50 winter peak in 2035/2036. Transportation electrification is forecast to contribute 1,509 MW to the 50/50 winter peak in 2035/2036.
BTM PV is forecast to have a growing impact on 50/50 winter peak demand, reducing it by 316 MW in 2035/2036.
