General Motors has announced that the Chevy Volt will get 230 mpg for city driving, and probably around 100 mpg for combined city/highway driving.
The Volt obtains this performance, of course, through its use of a battery recharged from the grid. “230 mpg” means “230 miles per gallon of gasoline,” and ignores the coal or natural gas which in most cases will supply the recharging. The Electricity Fairy has not been coming around a lot lately.
A proper metric for a vehicle such as the Volt depends on what factors the buyer really cares about…
If your main concern is “energy independence,” then “miles per gallon of gasoline” is probably a reasonable criterion.
If your main concern is operating cost, then you need “total cost per mile,” based on a combination of gasoline cost and electricity cost.
If you worry that the world is going to run out of energy, you should be looking at “BTUs per mile.”
And if you really believe CO2 is going to destroy us all, then the metric you should care about is “CO2 emissions per mile.”
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