The Chevrolet Volt has been branded as a lot of things; GM's saving grace, the car of the future and a car for the environmentally conscious. The Volt has been GM's marketing focus, auto show crown jewel and technology test bed for years, so when an environmental group gave their baby a ho-hum ranking, it's no surprise they took it somewhat personally.
The American Council for an Energy-Efficient Economy publishes the Green Book, an online ranking of a car's environmental impact. Each car on the market is assigned a number based on how environmentally friendly they perceive it to be. The Volt came back ranked as the 12th greenest car of 2011, with a score of just 48 Green Points. You can compare that to the 54 points of the first place Honda Civic GX (with the compressed natural gas engine).
Chevrolet claims that the methods used to rank their Volt don't really give a fair view on how efficient the car actually performs. Because of the way the Volt operates, you could easily argue that point.
The Volt is pretty unique as far as hybrid cars go. Most hybrids, like the Toyota Prius, use a gasoline engine with an electric motor to boost efficiency. The Volt is essentially an all-electric car with a gasoline generator on board. This means that the electric motor is the only source of the car's power, and when electricity runs out, a generator will turn on to recharge the car's batteries.
The generator allows the Volt to drive beyond the range of the car's electric batteries. So, unlike the Nissan Leaf (which tied the first place Civic with a green score of 54) you could use it on long road trips or extended drives without having to spend hours recharging the batteries.
Chevrolet says their Volt can travel up to 35 miles before the gasoline engine needs to get involved.
The matter of ranking the Volt is so complicated that the EPA issued two unique miles per gallon figures for the car: 93 mpg using electricity and 37 mpg using gasoline. It's that gasoline figure that really hurts the Volt's green score, but Chevy argues that most people will be able to get to and from work without ever needing the gasoline safety net.
Chevy is so confident that Volt owners will only have to use the gas engine once in a while, that the car has been fitted with a reminder to let them know when the gas in the tank is exceeding its shelf life (about one year).
Rob Peterson, a GM spokesperson told Forbes, "... we lose against the Leaf because we have a gas engine. But you really have to look at how the car is actually used – their methodology doesn't add up."
No matter how you do the math, the Volt is still greener than most vehicles. Bottoming out the list for least green vehicle is Bugatti's 253 mph Veyron with 19 Green Points.