Car companies certainly play up that perception, whether through green-sounding names like the Nissan Leaf or through tools like Tesla's online emissions counter. Recently, however, analysts have been questioning just how green these green machines actually are. As Will Oremus notes in Mother Jones, the answer may depend in no small part on where you live ... and where your electricity comes from. After all, almost half of U.S. electricity production comes from coal, a dirty-burning product that releases carbon dioxide just like a gas engine. To make matters worse, burning coal also releases a variety of other noxious compounds, including nitrogen oxides and sulfur dioxide, which are significant contributors to acid rain.
Oremus notes that not every state relies heavily on coal. Some use nuclear power -- which opens another can of worms -- while others use more solar, hydroelectric, wind, and other renewable resources. In other words, the carbon footprint an electric car varies greatly from state to state. As, for that matter, does the pollution level of coal-burning plants, depending on the level of emission-scrubbing they do, and the relative "cleanness" or "dirtiness" of the coal they use.
Admittedly, when it comes to the green footprint of electrics, emissions aren't the entire story. After all, these cars use a host of rare earth minerals in their batteries; moreover, "vampire" drain, by which their batteries slowly lose charge even when the car isn't being driven, casts their incredibly high mpg equivalence into question. Ultimately, though, the questions surrounding electrics' emissions cast an interesting light on an even larger underlying problem: the patchwork of exemptions that keeps some of America's filthiest power plants in business -- and continues to get in the way of converting our nation over to genuinely greener electricity.
Bruce Watson is DailyFinance's Savings Editor. You can reach him by e-mail at firstname.lastname@example.org, or follow him on Twitter at @bruce1971.