DOE Rolls Back EV Fuel Math: Back to Basics After Court Smackdown
Published Date: 1/8/2026
Rule
Summary
The Department of Energy is rolling back a 2024 rule about how electric vehicles’ fuel economy is calculated, following a court decision. This change affects car makers who must meet fuel standards and takes effect January 8, 2026, with legal impact starting September 5, 2025. It means the way electric cars’ efficiency is measured will return to an earlier method, keeping things fair and clear for everyone.
Analyzed Economic Effects
2 provisions identified: 0 benefits, 0 costs, 2 mixed.
Reverts EV fuel-economy method
If you make light-duty vehicles, DOE is removing the March 29, 2024 revisions and returning to the prior method for calculating petroleum-equivalent fuel economy that the EPA uses to determine compliance with DOT CAFE standards. The change is effective January 8, 2026, and the court opinion had legal effect on September 5, 2025.
Restores numeric PEF values
DOE restored the prior petroleum-equivalency factor values used to compute EV petroleum-equivalent fuel economy, including a PEF of 82,049 Watt-hours per gallon for vehicles without petroleum-powered accessories and an example PEF of 73,844 Watt-hours per gallon when a petroleum accessory is installed. These values are reflected in the appendix examples and apply as the rule reads after removing the 2024 revisions.
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