Volt Mileage Claims Makes EPA Rethink Ratings Process

General Motors’ upcoming Volt plug-in gasoline-electric hybrid is an exciting concept that promises a green vehicle with a sports car attitude. General Motors has since announced that the Volt would achieve 230 miles per gallon. Is this really possible? Will these numbers apply to real life driving? The issue here is the numbers are not official U.S. Environmental Protection Agency (EPA) fuel economy estimates. The EPA hasn’t yet formalized any method of testing or rating plug-in hybrid vehicles or a new generation of electric vehicles.

Every vehicle that is officially on sale in the US carries EPA fuel economy ratings, which are designed to give prospective owners an idea of relative fuel cost in real-world driving as well as a way of comparing various models on equal ground. The ratings are listed in the EPA’s annual Fuel Economy Guide, at fueleconomy.gov, or on the window sticker of any new vehicle; they’re also used in figuring an automaker’s corporate average fuel economy (CAFE) and in assessing a gas-guzzler tax on some vehicles. But because vehicles like the Volt are still in development stages, they have not yet gotten the EPA’s rating. With a host of plug-in hybrids, electric vehicles (EVs), and extended-range EVs all expected to go on sale over the next several years, the agency needs to move quickly to put a framework in place for fairly rating these vehicles.

The EPA has in the past rated EVs in terms of kilowatt-hours per 100 miles, which typically yields a double-digit number somewhat like miles per gallon. Currently the EPA is working with manufacturers, the Society of Automotive Engineers (SAE), the State of California, the Department of Energy (DOE), and other groups to form a new standard for estimating and labeling fuel economy for vehicles with more than one energy source.

Cost per mile would of course make the most sense to economically minded buyers, but it would become confusing and difficult to compare from year to year because of unstable energy prices. This will all be part of the next round of fuel economy standards phased in beginning in 2012, to yield the federally mandated 35.5-mpg fleet-wide average by 2016. Regardless of what the true mileage for the Volt will be, GM highlighted one important point in the process: a new process for EPA ratings is needed; as the age of automobiles turns a new corner, the EPA must follow.