Tuesday, August 11, 2009

Chevy Volt To Possibly Get 230 MPG

GM made a big announcement that its upcoming Chevy Volt could get an EPA city rating of 230 miles per gallon. Sounds amazing, doesn't it? What doesn't look to be as amazing is the fact that the 230 mpg figure results from some magical calculations. The Volt is a range-extended electric vehicle, once the battery is drained it turns on its internal combustion engine and uses gasoline. GM says that the Volt can travel 40 miles before the battery is drained. At this point calculating the fuel economy rating of the Volt becomes complicated. The 230 mpg figure is only possible if the Volt completes the EPA's fuel economy test solely on electric power and then completes the test again powered by the gasoline engine. In the end the Volt ends up using .22 of a gallon of gas to travel 51 miles, resulting in the 230 mpg figure. But this completely ignores the electrical energy used up. Like all things in life, it's not free either. And most likely comes with emissions as well. The GM press release also states that the Volt will use up 25 kilowatt-hours of electrical energy to travel 100 miles in the city. Thanks to this handy chart 25 kilowatt-hours contain the same amount of energy as 3/4 of a gallon of gas. This means that in pure electric mode the Volt would only travel 134 miles using the same amount of energy that's in a gallon of gas, thus cutting down the 230 mpg figure to 134. And since the Volt's battery is only good for 40 miles, the last 60 miles would be powered solely by gasoline. GM expects the Volt to achieve about 50 mpg when the battery runs out.

While the Volt is a fascinating concept that is poised to change how people commute daily, GM's 230 mpg quote looks to be powered by hype.

The breakdown of Volt's EPA test come from here.

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