2007 Detroit Auto Show: Chevrolet Volt Plug-in Hybrid Concept

You can tell fuel efficiency is a big deal when Detroit’s largest automaker makes its biggest surprise unveiling in years a plug-in electric hybrid vehicle called the Chevrolet Volt. The small coupe is definitely in GM's production pipeline. There’s just one little problem: The battery technology that will make this car run doesn’t exist yet.

That may seem like a big problem, but with the speed in battery development — think how much smaller your laptop is now than it used to be, and how much longer it lasts — we could see this happening in the project in a two- to three-year time frame. A small gas generator — that you would fill up at the gas station — will recharge a string of lithium batteries that line the floor of the car and power it after it's run its initial charge from being plugged in at a regular 110-volt outlet at home.

Theoretically, the vehicle could get up to 150 mpg with a range of 640 miles, but there are still the energy costs of plugging the car in at home. Imagine paying those Christmas light bills all year long — and that’s still a wild guess. We love GM’s boldness here, and it certainly one-ups Ford’s Airstream hydrogen plug-in hybrid concept with its even shakier production likelihood. If the Volt is produced, it will certainly have Toyota taking the Prius back to the drawing board.