Getting behind the wheel of new electric vehicles has become a signature move for self-proclaimed “car man” President Joe Biden. But his choice of car has put some climate advocates on the brakes.

Biden has touted the future of electric vehicles throughout his presidency and even trialled a few, including the Ford F-150 Lightning And Hummer EV.

Those EVs have one thing in common: their batteries.

The battery of the Ford Lightning weighs 1,800 poundswhile the Hummer EV’s 2,923-pound battery alone weighs more than a gasoline-powered Honda Civic. And that extra weight has some negative consequences.

Related: The 6 Most Luxurious Electric Cars on the Market That Will Make You Want to Skip Gas

For starters, heavier cars mean more wear and tear on the roads. The head of the National Transportation Safety Board has also warned that large electric cars like the Hummer can increase the risk of serious injury or death for pedestrians and other drivers in a crash.

Then there are the climate issues. Larger batteries need a lot of critical minerals, which they mostly do produced with energy from fossil fuels. It also takes a lot more electricity to power those cars, and the power grid is still heavily dependent on fossil fuels.

So while the Hummer EV may get better for the climate as more renewables come online, for now, it emits more carbon per mile than the most efficient petrol cars.

All of these factors have led some climate advocates to appeal to the Biden administration and automakers building and promoting smaller electric cars. But others would like to see federal funding go to it another overlooked climate solution: public transport.