If self-driving cars take off, people might wind up taking more car trips, which could lead to Americans consuming more energy than if self-driving cars rarely leave the lot, according to a government report.

Today, transportation — including passenger vehicles, buses, and commercial trucks — accounts for about a third of energy use in the US, according to the Energy Information Administration (EIA). (It’s also the number one source of carbon emissions, YaleEnvironment360 reports.) By 2050, the EIA predicts that transportation will probably use less energy in the form of gasoline and electricity, thanks to cleaner and more efficient vehicles. But how much less? That depends, in part, on how popular self-driving cars become, according to a recent EIA report.

To find out how the future of transportation could play out, researchers compared three different scenarios. In one, self-driving cars only make up about 1 percent of new car sales in 2050, they’re mainly used for ride-sharing, and they’re gas-powered. In the two other scenarios, self-driving cars make up nearly a third of new car sales, they’re mainly privately owned, and they’re either electric cars or hybrids.

The researchers calculated that the perks of hands-free driving could prompt people to hit the road more than they would if self-driving cars don’t become popular. That’s because autonomous vehicles might discourage people from taking local public transportation or allow people without licenses to drive. For the scenarios where autonomous cars are much more popular, the researchers calculate that there would be a 14 percent increase in the number of driven miles in 2050, from 3.3 trillion miles to 3.8 trillion, compared to scenario number one. That would up energy demand by 4 percent compared to an autonomous car-lite future, the article says — even if the new autonomous vehicles are electric or hybrids.

Of course, we don’t know what the future will look like. After all, the Environmental Protection Agency is pushing to relax regulations on automakers, which could mean a future in which the transportation sector guzzles more energy, no matter who’s driving.