Regional Electric Peak Load Forecasts for Maine: Implications of Electrification and ISO-NE CELT Forecasts (2024-2033)
On behalf of the Maine Office of the Public Advocate (OPA), Synapse developed regional summer and winter electric peak load forecasts for Maine for the 10-year period from 2024 to 2033 to inform the evaluation of future grid investment needs. The analysis focuses on peak demand under extreme weather conditions and explicitly incorporates the impacts of heating electrification, electric light-duty vehicles, electric medium- and heavy-duty vehicles, and distributed energy resources.
The forecasts show that Maine’s electric system is rapidly transitioning to a winter-peaking profile driven primarily by electric space heating. Northeastern Maine and Central and Western Maine are already winter-peaking, and Southeastern Maine is projected to become winter-peaking around 2028. Winter peak growth substantially exceeds summer peak growth across all regions, with heating electrification accounting for the majority of future peak increases, while electric vehicle charging contributes a smaller and more manageable share, particularly with managed charging. Comparison with ISO-NE’s 2024 and 2025 Capacity, Energy, Loads, and Transmission (CELT) forecasts identifies material regional and methodological differences: the 2024 CELT appears to overstate future peak loads in southern Maine while understating winter peak growth in colder northern regions, whereas the 2025 CELT reflects methodological improvements, particularly related to EV adoption, but still projects higher winter heat-pump-driven peak loads in Central and Western Maine than Synapse’s analysis, in part due to outdated assumptions about cold-climate heat pump efficiency.