EPA Seeks New Ways To Measure And Explain Fuel Economy

October 1, 2009
2011 Chevrolet Volt

2011 Chevrolet Volt

Like that old gray mare the kids keep talking about, fuel economy standards ain't what they used to be. We've seen this recently with General Motors' announcement of a 230 mpg rating for the Chevrolet Volt. We've also seen it with the Fisker Karma sedan, which announced a much more modest fuel economy of 67 mpg. In the context of conventional, combustion-engined cars, those figures are pretty eye-popping -- but of course, they're not quite what they seem. The EPA is working to fix that.

The problem with the Chevy Volt, the Fisker Karma, Jaguar's "Limo Green" concept, and other new-tech vehicles is their drivetrains, which center around battery packs that power electric motors that propel the car. Those battery packs offer varying ranges depending on their size, composition, and other factors; when the batteries are drained, a combustion engine kicks in, but that engine doesn't directly power the wheels. Instead, it acts as a generator to charge the battery pack that drives the electric motor that drives the wheels. In other words, although these vehicles are technically hybrids -- incorporating both electric batteries and combustion engines -- propulsion comes only from the electric sources.

So, if a Volt driver travels less than 40 miles per day (40 miles being the Volt's expected range per-charge), he or she could plug-in the Volt every night, recharge the battery, and never touch gas, which essentially renders fuel economy as we know it a moot point. The further drivers go beyond a car's electric-only range and rely on their combustion engines, the lower their fuel economy. Interestingly, the situation seems far less complicated for electric vehicles that don't use combustion engines at all: substituting "miles per charge" for "miles per gallon" is pretty straightforward, no?

The Environmental Protection Agency is looking at ways to make fuel economy ratings in advance-tech hybrid vehicles clearer to consumers. In a letter released yesterday, the EPA said it would "initiate a new rule-making to explore in detail the information displayed on the current fuel economy label and the methodology for deriving that information." As such, it's seeking input from automakers, scientists, and others about ways to deliver fuel economy information in a way that makes sense to the general public.

So far, the one that seems most sensible to us -- and the one that prompted the EPA's letter -- comes from Israel's ETV Motors, which is working on at least one new-tech vehicle with a powertrain similar to the one in the Volt. ETV suggests that customers be given three pieces of information on the window sticker: "the E.V.'s all-electric range, its energy efficiency in electric mode (expressed in miles a 10 kilowatt-hours) and, for plug-in hybrids, its fuel efficiency when the internal-combustion engine kicks in." The folks at Norway's Think have suggested something more akin to the Energy Star ratings seen on home appliances, paired with an estimation of the annual cost to drive vehicle.

Neither of those ideas is perfect, but they seem like pretty good places to start the discussion. If you've got some great ideas of your own, feel free to share them -- if not with us, then perhaps the EPA.


The Car Connection
See the winners »
The Car Connection
Commenting is closed for this article
Ratings and Reviews
Rate and review your car for The Car Connection
Review your car
The Car Connection Daily Headlines
I agree to receive emails from The Car Connection. I understand that I can unsubscribe at any time. Privacy Policy.
Thank you! Please check your email for confirmation.