Yes, your Tesla Model Y or BYD Song can zip down the road without emitting a single gram of carbon dioxide. But you’re probably still adding CO₂ to the atmosphere—because the “E” in your EV may well have come from fossil fuels. Worldwide, roughly 61% of electricity is generated by burning coal, natural gas, or oil. The graphic below offers a sense of how much each country relies on such fuels for power: The darker the box, the dirtier the grid. China exemplifies this dilemma. Its consumers buy more EVs than the rest of the world combined, but its coal-heavy energy infrastructure means that emissions at the power plant offset a lot of the savings at the tailpipe. As Kristen Siemen, General Motors chief sustainability officer, tells Fortune: “The only way to get to zero-emission driving is to decarbonize the grid.”