Edmunds.com Recommends Shift From MPG Emphasis

Edmunds.com Recommends Shift From MPG Emphasis

By Bill Visnic November 16, 2009

Edmunds.com, parent of AutoObserver, late last week submitted a recommendation to the U.S. Environmental Protection Agency and Department of Transportation to make fuel-economy information on new-vehicle window stickers more useful by shifting to a cost-of-energy figure rather than today's emphasized miles-per-gallon numbers.

  Edmunds.com believes beginning to focus on annual or monthly energy-cost figures will better prepare consumers and the industry for the increasing number of alternative-propulsion vehicles coming into production. Fully electric, extended-range electric and plug-in hybrid models all will rely less (or not at all) on burning liquid fuel - and translating their energy usage to MPG equivalents so far has proven to generate unrepresentative numbers that make for difficult comparisons between different types of vehicles.

"Consumers have used the existing MPG ratings primarily to get a sense of the relative cost of operating a vehicle on a day-to-day basis," said Edmunds.com CEO Jeremy Anwyl. "However, using energy equivalents can easily cause consumers to draw erroneous conclusions."

Anwyl said to consider the case of the recently announced 230 mpg-equivalent fuel economy for General Motors Co.'s Chevrolet Volt extended-range electric vehicle or the full electric Mini E from BMW AG's Mini, rated at a 99 mpg equivalent. Comparing to the 50-mpg rating of Toyota Motor Corp.'s 2010 Prius hybrid-electric car, casual comparison would lead to the belief the Mini E, for example, is half as costly to fuel as the Prius, or the Volt, with more than four times better mpg-equivalent fuel economy, would have less than one-quarter the fuel cost of the Prius.

But using a propriety formula using data points similar to its well-established True Cost to Own calculator, Edmunds.com statisticians have generated a list of monthly fuel costs that enables more accurate comparison of energy costs for all types of vehicles.

Using the formula, researchers determined that while the Mini E and Volt are (or will be) some of the most economical vehicles to operate, their cost savings are not proportional to their MPG-equivalent ratings. Compared to the 50-mpg 2010 Prius' monthly fuel cost of $66.78, the 230 mpg-equivalent Volt will cost $53.55 per month to fuel, Edmunds.com calculates, while the 99 mpg-equivalent Mini E costs $49.39.

"Looking at this analysis we find that electric vehicles do enjoy a cost advantage over their counterparts powered with other technologies--but this advantage is nowhere near as great as the proposed EPA ratings would imply," Anwyl said.

Little would have to change with today's window stickers. The EPA already lists the estimated annual fuel cost for every new vehicle and has developed the methodology to do so. Edmunds.com recommended to the agencies that the emphasis on window stickers simply be shifted to highlight this figure. Edmunds also suggested automaker marketing that uses EPA figures also should be required to use EPA-generated estimates for monthly fuel costs.

Using its own formula, Edmunds.com has compiled a list of monthly fuel costs for all 2009 and 2010 light vehicles. That list can be found here. - Bill Visnic, senior contributing editor

Chevrolet Volt image courtesy General Motors Co. 

Bill Visnic:  is an AutoObserver Senior Editor. Follow @AutoObserver on Twitter