The EPA isn’t so sure.

USA Today reports, “The concept of judging fuel efficiency on electric cars by the ‘miles per gallon’ they consume is dying a slow death. The EPA and other government agencies are working on a formula that will accurately tell people how fuel efficient electric vehicles are — but since those cars don’t use gas, miles per gallon doesn’t make any sense.”

GM and Nissan based their claims, the New York Times explains, “on a draft Environmental Protection Agency standard for plug-in hybrids and battery cars. But the agency says that work isn’t complete, and it is searching for meaningful ways to present the information to car buyers on the window sticker.”  The agency may never use the standard GM and Nissan used to back up their claims.

But developing a new standard is a controversial process. The Times reports, “Automakers and environmentalists interviewed have their own take on what an ideal E.V. window sticker would look like.” More

While the exact method of testing is not known we do know that the EPA agreed to a testing method that will at least achieve a three digit mileage number.

“It’s a huge milestone to beat 100 mpg. It’s bragging rights,” said Rebecca Lindland, an analyst at Global Insight Inc. in Lexington, Massachusetts. “To many people, GM is just about gas-guzzling SUVs. They never get credit for fuel economy. If Toyota were doing the Volt, they would be having parades and waving flags.”

The EPA will confirm the method of testing when it gets finalized.  Spokeswoman Catherine C. Milbourn said in a statement that the agency “hopes to have a final policy soon”.

Reaching past 100 miles per gallon on the Volt would be a boon to GM since all automakers have to raise their fleet to 35 mpg according to CAFE standards by 2020.

Depending on different assumptions on how much fuel is used the Volt could get an EPA rating between 120 mpg and 200 mpg.

Source: Bloomberg

What the EPA decides can have an important impact on how the Volt gets it’s ratings.  The Volt does have an electric motor and an internal combustion engine. That sounds a lot like the Prius hybrid.  The difference between the two is that the prius uses it’s electric motor at low speeds under light load and then kicks in the gas engine to turn the wheels.  On the Volt the electric motor is used exclusively to power the car.  The gas engine is used to power a generator to recharge batteries that will extend it’s range.

Some people have been saying that the Volt can make it through the current EPA testing with the ICE on only 15% of the time.  Using those numbers it would have an EPA estimate over 100 miles per gallon.  The issue GM has with the EPA right now is that the EPA wants the Volt to finish the test with it’s batteries at full charge instead of drained.  Under those circumstances the ICE would have to run constantly to recharge the batteries giving it a measly 48 mpg.

GM argues that since the Volt can be plugged into any 110 wall outlet that many people will never use gas on a daily basis.  Their main concern is that if the mpg rating is too low (lower than the Jetta and equal to the Prius) many people will not even consider the Volt since it’s price tag is in the mid 30′s right now.

Source: MotorTrend

I personally don’t think this will be an issue for the Volt.  It’s a car that is only powered by an electric motor, that makes it unique among the green cars (with the exception of the Tesla Roadster).  The EPA is doing a rating of miles per gallon, and electricity isn’t measured in gallons.  So if they’re going to crowbar the Volt into their current testing standards then this is what they have to do.

They probably should come up with something new though for cars like the Volt.  We’ll be seeing more of them in the future.