As part of a major overhaul of its annual load forecasting process, ISO-NE has significantly scaled back its electrification forecast for electric vehicles and heat pumps.
Prior forecasts relied heavily on state EV targets to estimate load growth due to a lack of data on EV adoption. ISO-NE has compiled data over the past few years, enabling it to better estimate the actual adoption rates in the region, said Victoria Rojo, supervisor of load forecasting and system planning at ISO-NE.
“Comprehensive vehicle registration data has indicated that prior forecasts have exceeded actual EV registrations,” Rojo told the Planning Advisory Committee on March 19.
ISO-NE has indicated its 2024 Capacity, Energy, Loads and Transmission (CELT) report overestimated the adoption of personal light-duty vehicles by more than 70%. As a result, the RTO is reducing its adoption forecasts for all classes of electric vehicles.
To a lesser extent, the RTO also has reined in its forecast for heat pump adoption in the region, reducing its 2025 adoption expectation for Connecticut by 30% and for Massachusetts by 15%. The changes aim to account for “state policies, goals and [the] best available historical installation data.”
While ISO-NE still expects heating and transportation electrification to increase substantially long-term, the updated adoption numbers significantly decrease the energy forecast for the upcoming decade. In its draft CELT forecast, ISO-NE reduced its annual net energy projection for 2033 by 8.2%, from 140,001 GWh to 128,460 GWh.
The RTO also cut its summer peak load projection for 2033 to 26,663 MW, a 1.4% reduction, and dropped its winter peak projection to 24,440 MW, an 8.7% reduction.
This is the second straight year ISO-NE has scaled back its demand forecasts. In 2024 it reduced its 10-year summer peak load forecast by 1.8% and its winter peak by 2.5%. (See ISO-NE Decreases Its 10-year Peak Load Forecast.)
An ISO-NE study looking at 2032 — which relied on the elevated 2023 CELT forecast — found limited risk of shortfall on the New England grid, with the greatest risks coming during extreme winter weather scenarios. (See ISO-NE Sees Little Shortfall Risk for 2032.)
The electrification adoption changes are one component of a revamped forecasting methodology ISO-NE has rolled out for its 2025 CELT report. The new modeling capabilities will enable the RTO to estimate hourly power demand in each load zone more than 20 years into the future. The modeling will rely on zonal, county-level forecasts of electric vehicles, heat pumps and behind-the-meter solar.
“Each forecast component (base load, EV, HP and BTM PV) reflects coincident weather over a 70-year simulation period and are combined into forecasts of net and gross load for each zone and the region,” Rojo noted.
The new methodology also introduces “climate-adjusted weather data reflecting 70 weather years,” Rojo said. ISO-NE previously had not included the effects of climate change in its CELT forecasts.
The modeling also uses energy efficiency as an input to the model, eliminating the need for a separate energy efficiency forecast.
The RTO plans to publish its final CELT forecast in May.
