Does coal mean electric cars are bad? No, it's the other way around.

Coal may make electric cars dirtier to run in the short term, Voelcker writes. But, in the long term, its electric cars that help make the case for rendering coal obsolete.

Every so often, electric-car skeptics will attack the idea of using grid electricity to power a car by bringing up coal.

"Yeah," the argument goes, "but you're just burning coal instead of gasoline in your electric car--so how's that any better?"

There is, of course, a fair amount of science that shows it actually is better when measured by wells-to-wheels carbon emissions.

The most recent study came from the Union of Concerned Scientists last year, complete with a neat little map looking at each state's electric grid.

The conclusion: Even in the few states with the very dirtiest grids, driving a mile on grid electricity is barely worse than the most fuel-efficient non-hybrid car (roughly 34 mpg). 

And in states with the cleanest grids, there's no combustion-engine vehicle that can match an electric car for low carbon emissions.

A landmark 2007 study jointly produced by the Electric Power Research Institute (the research arm of the electric utility industry) and the Natural Resources Defense Council comes to broadly similar conclusions.

It's also worth noting that the majority of electric cars operate in states with very low-coal grids: California, Washington, and New York among them.

And most state grids are slowly getting cleaner.

Natural gas is cheap and readily available, more wind and solar are being added, and some of the most antiquated coal plants will be shut down or converted to natural gas in the years to come.

But what really sparked this article was an article in Mother Jones magazine, entitled "How Green is A Tesla, Really?"

It's conceptually quite similar to one we published in May by David Noland, who extensively analyzed whether his 2013 Tesla Model S pollutes as much as a sport-utility vehicle.

Hint: It doesn't.

But the Mother Jones piece contained this wonderful concluding paragraph:

To use the nation's reliance on dirty coal as an argument against electric cars is to get things backward. Rather, the prospect of making cars far greener than they are today should count as yet another argument against the nation's continued reliance on dirty coal.

We couldn't have said it better ourselves.

We should note, however, that for certain non-carbon smokestack emissions--including nitrogen oxides (NOx) and sulfur dioxide (SO2)--that mile driven in an electric car is worse than one in a modern gasoline car.

[hat tip: John C. Briggs]