11 mileage-obsessed questions

GM plans to sell the Chevy Volt plug-in hybrid by 2010.

•  Send feedback to Money Magazine

A. You are probably talking about plug-in hybrid electric vehicles, or PHEVs. Like pure electric cars, these can be recharged via a wall socket. Unlike pure electric cars, PHEVs also have a gas engine that starts as needed to either move the car or recharge the battery, so you won't be stuck as you are when your cell phone dies.

The fuel economics of PHEVs exceed those of the current crop of hybrids. They can run up to 40 miles on battery alone, and the cost per mile can be about a tenth that of a gas-powered car. Toyota is hoping to have its Prius PHEV to market by 2010, and GM plans to sell its Volt PHEV by then too.

The big question will be cost; the battery is quite expensive so far. "We're talking thousands of dollars," says Kelley Blue Book's Nerad. "The payback period could be very lengthy." The popularity of PHEVs will depend to a large degree on how big a tax credit the government offers.

NEXT: Doing the math