WASHINGTON (Reuters) - The U.S. Energy Department (DOE) on Tuesday is set to unveil final rules that will significantly soften its proposal that would have slashed electric vehicles' (EV) mileage ratings to meet government fuel economy requirements in 2027, sources said.

In April 2023, the Energy Department proposed rules that automakers said would "devalue the fuel economy of electric vehicles by 72%" in 2027 and lead to significantly higher Corporate Average Fuel Economy fines for some automakers.

The final rule will gradually reduce EV mileage ratings through 2030 and by 65% in total giving automakers more time to adjust, the sources said.