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Krauss in Forbes: GM Claims for Volt Questionable

General Motors' claims of an estimated 230 miles per gallon gas efficiency for its pricy new Volt are far from realistic says Professor Michael Krauss in a recent article in Forbes magazine.

The Volt is scheduled to go on sale in 2010 for an estimated $40,000 per vehicle. By Krauss's reckoning, GM presumably calculated the 230-mpg figure using Environmental Protection Agency draft guidelines for calculating gas consumption of "plug-in" vehicles.

"There is no obviously correct way to compare the efficiency of electric vehicles—whether 'strong hybrids' like the Toyota Prius and the Ford Escape or 'plug-ins' like the Volt," says Krauss. By analysis, Krauss illustrates that in normal use, the Volt's actual efficiency in high-electricity-cost states could drop to an equivalent of 90% less than GM's touted mileage estimate.

"The federal government now owns a controlling interest in GM. Will it promulgate EPA final guidelines that authorize the Volt's 230-mpg claim?" Krauss asks. "Or will Washington force GM to disclose how poor a choice this 'game changer' is for almost everyone."

General Motors' Game-Changing Bid, Forbes, September 16, 2009. By Michael I. Krauss.

"For plug-ins, however, the mileage measurement apparently authorized by the EPA draft guidelines is unintelligible. The Volt, for example, has enough electrical storage to travel 40 'ideal' miles (probably closer to 30 miles in real conditions) on battery power alone. GM claims this range is enough to allow 75% of Americans to commute to work and back. If a Volt owner were to forever restrict her driving to trips of less than 30 miles between charges, the Volt would give her not the claimed 230 mpg, but 'infinite' miles per gallon; the car might, theoretically, never need gasoline. This alone makes a mockery of the draft guidelines, which assume that at some point the Volt will be driven by its tiny gas engine.

"Then there's the cost of the charge. Since the Volt must be plugged in to recharge its battery, the draft guidelines factor in 11 cents per kilowatt-hour (current kwh prices range from 8 cents in North Dakota to 20 cents in Connecticut). GM estimates that the Volt will require 10 kwh for one complete charge (40 'ideal' miles, 30 'real' ones), or 25 kwh for every 100 'ideal' miles electrically driven. At 11 cents per kwh, 100 'ideal' miles of electric driving would cost the driver $2.75 ($2 in North Dakota, $5 in Connecticut). Since 87-octane gasoline currently costs $2.75 per gallon, one might say with a straight face that the Volt can theoretically travel 100 miles for the price of one gallon of gas. That is the equivalent of 100 mpg--60% less than GM's claimed 230.

"It gets worse. What if the owner drives more real miles than 30? The Volt's 1400cc gas engine must take over--not to drive the wheels, as other cars’ engines do, but to recharge the battery so that battery can power the electric motor that drives the wheels. What an inefficient torque delivery system! The Economist calculates that one should expect no more than 20 mpg with gasoline."

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