GM to make all-EV version of Volt

It's the next step for the Volt, a car the company says can run 40 miles on a charge from a standard home power outlet. After the battery wears down, a 1.4-liter four-cylinder internal combustion engine takes over and generates electricity to power the car.

It's due to go on sale this fall at a cost of about $40,000, before tax credits.

Lutz would not say exactly when the pure-electric version would make it into showrooms, but said it would be "technologically trivial" to switch out the internal combustion engine.

Lutz told reporters at the Detroit auto show that GM could quickly expand the Volt's battery pack and take out the engine to build a fully electric car similar to Nissan's Leaf.

The Leaf, also to go on sale in the U.S. late this year, can get up to 100 miles on an electric charge but must be recharged or have a new battery installed to go any further.

The Volt, Lutz said, eliminates "range anxiety" as the car gets close to depleting its batteries.

But there may be a market for pure-electric vehicles for people who travel less, or GM could need it to meet government fuel economy regulations, he said.

"Once you've done the Volt, pure electric is trivial. You just leave some parts out," Lutz said.

Lutz also said electric vehicles may not get the stated range on fully electric power because of weather, atmospheric conditions, terrain and driving habits. He said he had a Volt during the Thanksgiving weekend and got only 28 miles on full-electric power because of the cold weather.

"It varies a lot more than the range variation with a gasoline-powered car depending on your driving style," Lutz said.

The Volt equipped with the internal combustion engine was unveiled three years ago. Once it goes on sales later this year, it will qualify for up to $7,500 in tax credits.