Driving an electric car feels good: You’re not burning gasoline, and you’re avoiding its attendant ills, like poisoning your community and contributing to climate change. But, when you take into account where the electricity that powers your car comes from, it turns out that those warm fuzzies might be baseless.

A new study published in Proceedings of the National Academy of Sciences shows that if you live in a coal-dependent state, driving an electric vehicle might make your net effect on the environment and public health worse than if you had just stuck with a gas-powered vehicle. A team from the University of Minnesota compared cars powered by 10 different gasoline alternatives. The AP’s Seth Borenstein reports:

The study finds all-electric vehicles cause 86 percent more deaths from air pollution than do cars powered by regular gasoline. Coal produces 39 percent of the country’s electricity, according to the Department of Energy.

But if the power supply comes from natural gas, the all-electric car produces half as many air pollution health problems as gas-powered cars do. And if the power comes from wind, water or wave energy, it produces about one-quarter of the air pollution deaths.

Hybrids and diesel engines are cleaner than gas, causing fewer air pollution deaths and spewing less heat-trapping gas.

But ethanol isn’t, with 80 percent more air pollution mortality, according to the study.

The takeaway? In many parts of the country, electric cars may be … symbolic, at least at the moment. But they will make more and more sense as coal dies out and America’s energy system continues to get greener.

“Unfortunately, when a wire is connected to an electric vehicle at one end and a coal-fired power plant at the other end, the environmental consequences are worse than driving a normal gasoline-powered car,” Ken Caldeira, a climate scientist with the Carnegie Institution for Science, said in an email to Climate Central. Caldeira is unaffiliated with the study, but is working on similar research. “But electric vehicles are still good because they move us down a path toward a future near-zero emissions energy and transportation system,” he said. “Unfortunately, given the way electricity is generated in the U.S. today, the first steps down this path to lower pollution involves increases in pollution.”

Burning coal for electricity is responsible for a huge amount of America’s air pollution, and it’s the single biggest source of climate change — causing CO2 pollution in the country. Recognizing this, the Obama administration has proposed rules to crack down on coal plant pollution, which should have the effect of pushing some utilities toward cleaner energy. Meanwhile, the natural gas boom is already making coal an uneconomical source of power for utilities.

So, coal is already on the decline. And that’s good news for all those aspiring Tesla drivers out there.