FILE PHOTO: Electric vehicle chargers are shown in a shopping center parking lot in Oceanside, California, U.S.,October 19, 2023. REUTERS/Mike Blake/ File Photo

By Jonathan Stempel

(Reuters) -A U.S. appeals court on Friday voided a Biden administration-era rule that changed the calculation of the petroleum-equivalent fuel economy of electric vehicles, a victory for 13 Republican state attorneys general who said the rule overstated EVs' efficiency.

The 8th U.S. Circuit Court of Appeals in St. Louis said the Department of Energy exceeded its authority by deciding to phase out during the 2027 to 2030 model years a "fuel content" factor that artificially inflated EV fuel economy, rather than eliminating that factor.

Writing for a three-judge panel, Circuit Judge Duane Benton said the department also failed to provide notice of the range of alternatives it was considering when it sought comments for the March 2024 rule, depriving commenters a chance to provide "informed criticism."

Petroleum equivalency is used in calculating whether manufacturers meet the Department of Transportation's corporate average fuel economy (CAFE) standards.

While the final rule was watered down from an earlier proposal, the Energy Department said keeping the fuel content factor would likely encourage EV production in the near term, while "accelerating the widespread adoption of EVs in the United States during this pivotal time."

Led by Iowa, the 13 states and the nonprofit American Free Enterprise Chamber of Commerce said overstating EVs' efficiency caused harm by allowing manufacturers to produce less-efficient gas-powered vehicles, thereby increasing greenhouse gas emissions, and still meet CAFE standards.

They also said encouraging EV sales makes it more costly to maintain roads, because EVs are heavy and cause more wear and tear.

Neither the Energy Department nor the office of Iowa Attorney General Brenna Bird immediately responded to requests for comment.

Arkansas, Florida, Idaho, Kansas, Mississippi, Missouri, Montana, Nebraska, Ohio, Oklahoma, Texas, and Utah also opposed the rule.

Oral arguments took place five days before Republican President Donald Trump began his second term.

The case is Iowa et al. v. Wright et al., 8th U.S. Circuit Court of Appeals, No. 24-1721.

(Reporting by Jonathan Stempel in New YorkEditing by Rod Nickel)