Chevrolet introduced their 'Volt' concept car at this year's Auto Show in Detroit. It has the capacity to run on only electricity for up to forty miles. If the battery runs out of power, then and only then will the gas engine kick in. The gas engine works to recharge the electricity so the vehicle can run on only the battery again. On one tank of gas, the car should be able to travel around 640 miles, and get triple-digit gas mileage. The car can be charged with a normal 110-volt plug-in that you would find in your house.