Observers said advertising the Volt’s fuel economy allows GM to bring attention to its products and tout efforts to improve the efficiency of its overall fleet, with one analyst calling triple digit mileage “bragging rights.”
Is the GM Volt mileage claim legit?
WARREN, Mich.–General Motors’ announcement on Tuesday that it expects that the Chevy Volt will get an eye-popping 230 miles per gallon begs an obvious question: how can the mileage of electric vehicles be compared to gasoline cars?
A common way of doing comparisons is converting the embedded energy in gasoline to batteries, which a 2000 Department of Energy rule does in addition to considering the efficiency of the overall energy delivery system.
(Credit:Martin LaMonica/CNET)
In the case of the Volt’s city mileage, fuel economy will begin to drop off when drivers go beyond 40 miles before recharging. The Volt’s electric driving range was chosen specifically because U.S. Department of Transportation research shows that almost 80 percent of Americans drive under 40 miles a day.
In the EPA model GM has followed, those first 40 miles equate to “infinite mileage,” since it was charged from the grid and no gasoline was burned. But to consider electricity as infinite fuel efficiency can be misleading given that some energy–be it coal, natural gas, or nuclear–went into the delivery of electricity to charge the batteries.
For example, comparing the Volt to the Prius with that methodology is not useful, argued Darryl Siry, the former chief marketing officer at Tesla Motors and now a consultant withgreen-tech companies. By the EPA measure, it would appear that the Volt is many times more efficient than the Prius. But the 230 miles per gallon rating more accurately reflects how much gasoline has been consumed rather than the overall efficiency of the system, he said. “People will improperly conclude that the Volt is about five times more efficient that the Prius, which simply isn’t true,” Siry wrote.
Martin LaMonica is a senior writer for CNET’s Green Tech blog. He started at CNET News in 2002, covering IT and Web development. Before that, he was executive editor at IT publication InfoWorld. E-mail Martin.