Chevy Volt Under 230 MPG Banner

(Updated August 12) General Motors announced on Tuesday that the Chevy Volt could get a government in-city fuel economy rating of “230 miles per gallon.” While the potential for a three-digit mpg rating is grabbing headlines, figuring out what it means is another matter. What’s the significance of MPG in a vehicle which seldom or never uses gallons of liquid fuel?

“The main message is, oh my God, this is different,” Chelsea Sexton, a leading electric car educator and advocate, told Sexton is enthusiastic about the ability for plug-in cars to significantly reduce the use of petroleum—but said it’s hard to know what kind of efficiency any particular vehicle will achieve until the vehicle gets put to use in the real world.

The Environmental Protection Agency’s methodology for rating electric-drive vehicles is not finalized, and the official testing for the Volt will not occur until much closer to the vehicle’s launch in November 2010.

Potential Backfire

Nonetheless, General Motors launched an advertising campaign to promote the “230” figure, and was behind an unbranded website— (which now redirects to GM’s main Chevy Volt page)—and the distribution of hats and T-shirts on streets in several major cities. Fritz Henderson, GM CEO, said that the website and street campaign was an effort to win a new generation of buyers. “We need to relate to people between 16 and 30,” said Henderson in a live webcast on Wednesday . “They communicate differently and we need to make sure we plug into that. It’s going to change advertising and it’s going to change marketing and, over time, how we sell cars.” It’s uncertain if the Chevy Volt, expected to cost $40,000 (minus a $7,500 tax credit), will appeal to younger buyers.

Furthermore, there could be a potential backlash if final EPA numbers are signficantly lower than 230 mpg. To determine the 230 mpg number, GM loosely used the EPA’s preliminary plans. Those plans apply a complicated calculus of multiple methods for all-electric cars, plug-in series hybrids (also known as extended range electric cars), plug-in hybrids which blend gas and battery power, and conventional hybrids. Specific cars will also be measured multiple times for various modes of operation. GM used the most optimistic driving scenarios, in which the Chevy Volt was evaluated as an extended range electric car and was driven short distances and frequently recharged.

No Single Number

The multiple methodologies will yield multiple figures on the sticker, including kilowatt-hours per mile, miles per gallon equivalent, and in some cases, a straight mpg figure (as it is now for conventional hybrids). The numbers will also be adjusted for various energy efficiency credits—and as is currently the case, a different set of numbers will be used for the purposes of meeting federal efficiency standards. The numbers could easily confuse consumers—a critical risk in terms of consumer acceptance of plug-in cars.

Inside sources told that General Motors was concerned about making the announcement and experiencing a backlash from promising numbers which may not prove out in real-world driving.

The most accurate number for measuring plug-in car efficiency could be kilowatt-hours per 100 miles—although consumers have little experience with this metric and it’s uncertain how one plug-in car will compare with another for kWh/100 miles. GM expects the Volt to consume as little as 25 kilowatt-hours per 100 miles in city driving. Sexton believes that driving range, or the number of miles driven between charges or exclusively using battery power, is key.

Other all-electric cars, including the Mini E and the Tesla Roadster, are also claiming triple-digit mpg equivalent numbers. Using the preliminary EPA methodology, Nissan believes its all-electric vehicle, the Nissan Leaf, will achieve 367 miles to the gallon.