Chevy Volt. The burning question in many people’s minds is this:Â How muchÂ electricity does that electric portion of the trip use?Â GM answers that question (sort of) in a new press release:

“Applying EPA’s methodology, GM expects the Volt to consume as little as 25 kilowatt hours per 100 miles in city driving.”

That’s a number we can work with. 25 Kwh per 100 miles means the Volt will consumer 10 Kwh during its 40 mile electric-only portion of a journey. That’s 15 pounds of CO2– 20 if your utility uses exclusively coal-fired generation. Â To put it in cruder terms, the Volt takes 0.0975 pounds of coal (20 pounds of CO2 / 205 pounds everage CO2 per pound of coal) to travel those 40 miles, so it will go 410 miles on the electricity generated by a pound of coal.

Keep in mind, that most trips people make are short ones. DOT puts Americans’ mean trip length at 10 miles, where Volt excels. Even on a 40-mile trip, Volt uses an estimatedÂ 10 Kwh and no gas. That’s 15 pounds CO2 emissions compared to Prius’s 19 pounds. Even if you drive 100 miles at a time, your net fuel consumption would be (40*0) + (60*1/62.5)=Â 1.2 gallons +Â 15 Kwh. That still compares favorably with 1.9 gallons of gasoline in the 2010 Prius. On CO2 emissions, there’s little difference, though: Volt would emit about 39 pounds of CO2 for the trip compared to Prius’s 38 pounds.

As the trip lengthens, the difference in fuel consumption diminishes also. The 2010 Prius claims 53 mpg, while the Volt gets 50 mpg beyond its 40 mile electric range– a difference that’s statistically insignifiant. (You’d save 1.2 gallons over 1,000 miles in the Prius compared with Volt’s 20 gallons, assuming you drove like EPA does.)

The high price andÂ high minimum operating temperature will keep a lot of us from buying the Volt (how do you get to work when the temp is -30?), but it’s still a step in the right direction. Especially if (as the GM press release indicates) Volt’s generator is flex-fueled, meaning it can run on fuels other than gasoline.