Debate begins about fuel ratings on electric cars

DETROIT -- As the government hammers out how it will rate the fuel efficiency of hybrid-electric and all-electric vehicles, an Israeli company wants to make sure the U.S. gets it right.

The Environmental Protection Agency has a draft proposal for computing an efficiency rating using a "miles per gallon" scale but is not close to issuing a final ruling. It would be a rating buyers could use to compare various vehicles.

ETV Motors, a company that specializes in self-charging hybrid-electric propulsion systems for cars, has suggested in a letter to the EPA that the government consider a new multiple standard. CEO Dror Ben-David says ETV advocates a three-pronged rating for fuel efficiency: one number to show how far the car can go on a single plug-in battery charge, a second number to show how energy intensive the battery is, and a third for how much gasoline it consumes to drive a generator or the wheels when the battery runs out. Ben-David says the U.S. decision is important. "Most of the world looks at the United States as the standard provider and will adopt what the U.S. is doing."

Even though no plug-in electric vehicles have yet hit the market in significant numbers, debate has begun over efficiency claims. Using an EPA draft proposal, General Motors has forecast that its plug-in Chevrolet Volt electric car will be rated at 230 mpg (it will go 40 miles per plug-in charge before the gas engine comes on to generate electricity), though the EPA cannot confirm that. Nissan, using different numbers from the Department of Energy, claims its Leaf plug-in car, an all-electric with no engine to burn gas, will get the equivalent of 367 mpg.

Says Ben-David, "A single number is not good enough. ... It might be a bit misleading."

Jim Kliesch, a senior engineer for the Union of Concerned Scientists, says there are a variety of other ways the government could set a standard to cover plug-in electrics, but no option is simple.

He says they could measure the car's greenhouse gas emissions, a number that goes up when a vehicle consumes more gasoline or other fossil fuel. But that rating would also need to include how much carbon dioxide is emitted by power plants that generate electricity to recharge the car's battery when it is plugged in.