In its second year on the market, the 2012 Nissan Leaf is no longer the only battery electric vehicle. New entries from Mitsubishi and Ford, with others on the way, mean that at last we'll be able to compare the efficiency of plug-in vehicles of different sizes, shapes, and performance ratings.
But as it's powered solely by electricity—with no engine, no fuel tank, and no tailpipe—the 2012 Nissan Leaf is one of the cleanest, greenest cars you can buy. Unlike the 2012 Chevrolet Volt or Fisker Karma, with their range-extending gasoline engines, the Leaf uses only wall current to provide the power that turns the wheels and recharges its battery pack.
The EPA rates the 2012 Leaf at 99 MPGe, slightly better than the 94 MPGe rating for the Chevy Volt when it's running on its battery pack. The MPGe, or "Miles Per Gallon Equivalent," is a measure of energy efficiency meant to convey how far a vehicle can travel electrically on the amount of stored battery energy that represents the energy contained in a single gallon of gasoline.
While a mile run on electricity is usually far cheaper than a mile driven on gasoline, the difference varies considerably with the price per kilowatt-hour of electricity where the car is recharged. How much greener a Leaf is depends on the source of the energy used to create the electricity. A Leaf driven on power from the oldest, dirtiest coal power plants is still cleaner--on a "wells-to-wheels" carbon basis--than the average 25-mpg vehicle. Move up to the 50 mpg of a Toyota Prius, however, and in a small handful of areas (West Virginia and North Dakota are two with exceptionally dirty power, for instance), burning the gasoline in a Prius turns out to be slightly better overall.
The Leaf takes 7 to 10 hours to recharge a fully depleted lithium-ion battery pack if you've installed a 240-Volt charging station, which your Nissan dealer will help you arrange and purchase. On standard 110-Volt household current, a recharge can take up to 20 hours.