6:26 p.m. |Update
The American Council for an Energy-Efficient Economy, a Washington-based nonprofit group financed by foundations, electric utilities and state and federal agencies, released its annual list of the greenest vehicles of the model year on Tuesday. With five new models, this year’s list differs markedly from last year’s group.
The Leaf earned second place in this, the council’s 14th Green Book annual ranking. As for the Volt? It finished 13th, while topping the list for the eighth consecutive year was the Honda Civic GX, a limited-production model that burns compressed natural gas and that was expected to be available for retail sales nationwide in 2012.
In between are conventional hybrids and vehicles with old-fashioned gasoline engines. In fact, seven of the vehicles on the list use only gasoline engines.
How can this be? The council uses a novel, holistic method of calculating the slippery notion of greenness, one that expands on the fuel-efficiency and tailpipe-emissions considerations made by the Environmental Protection Agency.
“We consider not just what emissions are coming out of the tailpipe while the vehicle is running,” said Therese Langer, the group’s transportation director, in a telephone interview. “The E.P.A. would consider the Leaf a zero-emissions vehicle because electric vehicles have zero tailpipe emissions,” she said.
The so-called upstream emissions of an electric vehicle, however, can be substantial, she said, depending on where and how its electricity is generated. Electricity produced hydroelectrically, for example, will generally produce far lower carbon emissions than energy produced by burning coal.
But the council methodology also includes emissions associated with the generation of the electricity used to power a battery; the production of raw materials like steel and aluminum — and in an E.V.’s case, a lithium-ion battery unit; and its eventual disposal.
This was the first year in which the group incorporated emissions data associated with battery manufacture and disposal, for which it used the GREET model created by Argonne National Laboratory, an Energy Department lab. This explains why hybrids, which rely on power generated by electric motors and stored in batteries, claimed just three of the top 13 spots this year, compared with five in 2010.
The 13 greenest vehicles for 2011, from top to bottom, are:
• Honda Civic GX
• Nissan Leaf
• Smart Fortwo cabriolet and coupe
• Toyota Prius
• Honda Civic Hybrid
• Honda Insight
• Ford Fiesta SFE
• Chevrolet Cruze Eco
• Hyundai Elantra
• Mini Cooper
• Toyota Yaris
• Mazda 2
• Chevrolet Volt
For more information and the listings of the “Greenest” and “Meanest,” as well as best-in-class lists from the council, visit its Greenercars.org Web site.