Electric cars are squeaky clean, of course, in the sense that they don't burn gas. With no engine, no gas tank, and no exhaust, they're considered to be zero-emissions vehicles. But there's more to a vehicle's environmental impact than what comes out of the tailpipe. The Tesla doesn't run on air. It runs on electricity, which in turn is generated from a range of different sources, from nuclear fission to natural gas to the darkest, dirtiest fossil fuel of them all: coal.
So if you're going to stack a Tesla's per-mile emissions against those of a gas-powered vehicle, you'll need to start by looking at the composition of the electrical grid. Nationally, the grid is roughly 40 percent coal, 25 percent natural gas, 20 percent nuclear power, and about 10 percent renewable sources, led by hydroelectricity. So it's fair to say that your average Tesla is powered in large part by burning fossil fuels.
For any given Model S, though, the emissions per mile depend heavily on the mix of energy sources that go into your local grid. According to Tesla's own emissions calculator, if you're driving your Model S in West Virginia—where the power mix is 96 percent coal—you're spewing some 27 pounds of CO2 in a typical 40-mile day, which is comparable to the amount you'd emit in a conventional Honda Accord.
A market analyst named Nathan Weiss prompted spit-takes throughout the clean-energy world in May with an incendiary post on the financial-news site Seeking Alpha. The headline: "Is the Tesla Model S Green?" Weiss' answer: a resounding, math-heavy, 6,500-word "No." In fact, Weiss argued, the Model S is in many ways dirtier than a Jeep Grand Cherokee—and nearly as dirty as a Ford Expedition, one of the largest SUVs on the market. That's an extreme position, and large swaths of Weiss' argument were readily rebutted by electric-car advocates. Facing a barrage of criticism, Weiss soon revised his calculations, but still insisted that the Model S's effective CO2 emissions exceeded those of a smaller SUV like the Toyota Highlander.
