By Clint Williams

Imagine a day of running errands – grocery shopping, dropping off the dry cleaning, hauling the kids to T-ball practice – that doesn’t include a stop for gas. Now imagine a week. A month. Three months. Six months. A year. Five years.

That’s the promise of the Chevrolet Volt, a plug-in electric car expected in dealer showrooms November 2010. Powered by a T-shaped lithium-ion battery pack, the four-passenger Volt will be able to travel 40 miles on a charge.

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Video: Watch an overview of the Chevy Volt

That’s enough range for the bulk of daily driving, GM officials say, citing a U.S. Department of Transportation survey that found 76 percent of drivers commute 40 miles or less daily.

Drive a Volt and the only reasons for stopping at a QT are Slurpees and microwave breakfast burritos.

But those driving a Volt won’t be limited to in-town driving. A 1.4-liter, four-cylinder engine to be built in Flint, Michigan serves as an onboard generator, kicking in to charge the battery after 40 miles and giving the Volt the range of a conventional automobile.

The Volt isn’t a gasoline-electric hybrid, GM’s Cristi Landy points out repeatedly during a day-long introduction of the car last week at the Texas Motor Speedway near Dallas. The Volt, she says, “is an extended-range electric vehicle.”

Electricity powers the front-wheel-drive Volt all the time and at all speeds. Hybrid cars on the road now such as the Toyota Prius or Chevrolet Tahoe Hybrid use a combination of an electric motor and gas-powered internal combustion engine to make them go. The electric motor is used at low speeds or to boost acceleration. Once you’re up to freeway speeds, however, it’s the gasoline engine that is doing all the work. That explains why the EPA mileage estimates of the Prius are higher for city driving than for highway driving, the flip-flop of what you might expect.