Putting a label on fuel economy no easy task

  • 14-Apr-2010 10:09 EDT
The EPA's Christopher Grundler said at the SAE 2010 World Congress that new fuel-economy labels for vehicles are being studied.

Consumers have been getting vehicle fuel-economy information since the mid-1970s, but a label re-do may be coming if the U.S. EPA decides current mpg labels just aren't relevant to electrified vehicles.

"This is a challenging task before the EPA," said Christopher Grundler, Deputy Director in the EPA's Ann Arbor, MI, Office of Transportation and Air Quality, at the SAE 2010 World Congress being held in Detroit this week. The EPA's ongoing effort to develop a new fuel-economy label, he said, is all about helping "consumers make informed decisions."

Grundler, a participant of "The Battle Over Batteries: What's the Right Way to Compare Fuel Economy?" panel on Tuesday, said that the EPA—via a market research firm—is asking public focus groups in different regions of the U.S. what they like and do not like about today's EPA mpg labels.

People are in general agreement that simplicity is best.

But agreement can be a bit more difficult to find when focus groups, engineers, and others are asked what's the best way to convey mpg for a plug-in hybrid-electric vehicle (PHEV), an range-extended EV (EREV), or a battery EV (BEV).

Panelist Michael Tamor, Executive Technical Leader for HEV and Fuel Cell Vehicle Research at Ford, questioned whether a single metric could convey all the necessary information on an electrified vehicle's fuel-economy label.

A battery pack's contribution to mpg is relevant.

According to panelist Martin Klein, Engineering Director for Compact Power, an HEV's mpg improvement from electrification is 30-60%. He said a PHEV can realize a 50-100% mpg improvement from electrification, and an EREV's mpg increase can be 300% or greater.

"But a BEV has no internal-combustion engine. Therefore, there is no gasoline consumption. And the measurement of [the battery's direct] contribution to mpg becomes very complex," said Klein.

Peter Savagian, Engineering Director of Hybrid Powertrain Systems Engineering at General Motors, believes using a label with a mpg equivalent would be a mistake "because mpg equivalent is fictitious and requires a basic physics background to appreciate it."

One of Savagian's suggestions is to compare fuel and electricity consumption separately. That would mean mpg for fuel comparison and W·h/mi for electricity usage.

The EPA expects to have a proposal for a revised label this summer. Once that happens, formal public comments will be sought. A final determination is wanted by the 2012 model year, Grundler said.

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