Chevy Volt
Chevy Volt
Chevrolet

Americans bought 40,000 new electric vehicles in the first six months of this year — more than twice the number purchased during the same period last year. And that was after sales of plug-in cars tripled from 17,000 in 2011 to 52,000 last year.

Why are Americans so gung-ho on EVs? Caring about the environment is one reason. But the Energy Department highlighted another good reason on Friday when it released the plug-in sales data. From a department press release:

The eGallon, a quick and simple way for consumers to compare the costs of fueling electric vehicles vs. driving on gasoline, rose slightly to $1.18 from $1.14 in the latest monthly numbers, but remains far below the $3.49 cost of a gallon of gasoline.

“More and more Americans are taking advantage of the low and stable price of electricity as a transportation fuel, and that’s very good news for our economy as well as the environment,” said Energy Secretary Ernest Moniz. “As the market continues to grow, electric vehicles will play a key role in our effort to reduce air pollution and slow the effects of climate change.”

If you live in an area with low electricity prices, you’ll save even more by driving an EV. In Washington state, an eGallon costs just 84 cents.