Acadia National Park’s bus fleet soon will be carbon-free.

With a grant from the federal government, Downeast Transportation Inc., which provides public transportation at Acadia, will replace 21 of its propane-fueled buses with 23 electric buses.

Park visitors ascend a short path from a parking lot to the summit of Cadillac Mountain, one of the most popular spots in Acadia National Park. Ben McCanna/Staff Photographer

The $23.5 million grant from the U.S. Department of Transportation was announced Friday by Sen. Angus King and Rep. Chellie Pingree.

Paul Murphy, the executive director of Downeast Transportation, said that although it’s likely the electric buses will be used for ground transportation in Acadia solely during “Island Explorer” season from mid-June to early October, Downeast Transportation plans use to them on nearby routes year-round.

He expects to receive the electric buses in a few years.

“My guess is that … the buses will be delivered sometime between 2027 and 2028,” Murphy said. “Our hope is that they’ll be online for the opening of the Island Explorer season in June of 2028.”

The company’s current propane-fueled buses “will have reached the end of their useful life at about the same time as these buses arrive,” Murphy said. “What happens to them after that point will depend on their condition. We will be talking to our partners at the state and the park service to see if we hold on to some of them in other service or if they go out for disposal.”

The grant comes as Acadia is in the midst of constructing a new visitor’s center, where the Island Explorer bus will stop to pick up visitors on its way to other parts of the park. Acadia Superintendent Kevin Schneider said in a statement that he looks forward to implementing the project over the next few years.

The grant was funded by the USDOT’s Rebuilding American Infrastructure with Sustainability and Equity grants, which are funded by the 2021 Bipartisan Infrastructure Law.