Which car has the lowest carbon footprint?

Which new vehicle sold today has the lowest overall carbon footprint over its lifetime? It's the battery-electric Nissan Leaf, according  to a study set to be released this spring. 

Thomas B. Shea/Houston Chronicle/AP/File
A Nissan Leaf at the Houston Auto Show, held at Reliant Center in Houston, Texas. Among new cars, the Nissan Leaf has the lowest lifetime carbon footprint, according to a recent study.

Which new vehicle sold today has the lowest overall carbon footprint over its lifetime?

The answer, according to Automotive Science Group (via InsideEVs), turns out to be the Nissan Leaf battery-electric car.

In a study to be released this spring, The Automotive Peformance Index: Redefining Value in the North American Automotive Marketplace, ASG offers consumers "information to make responsible purchasing decisions" based on a car's environmental impact and its maker's record of social responsibilty.

Its site has a lengthy list of the methodology used to develop what it calls its Automotive Performance Index (API), including raw materials, assembly, transportation, consumer use, end-of-life recovery, and other issues including the carmaker's human-rights record.

Of all four-seat vehicles sold in North America for 2014, ASG calculated that the Nissan Leaf had the lowest environmental footprint over its entire life cycle.

Battery impacts

"Consumers can be confident," the group writes, "that the increased environmental impacts of manufacturing the battery electric technology is more than offset with increased environmental performance during operational life."

Moreover, while U.S. grid mix varies greatly by region, the average mix this year "is environmentally beneficial" when used to recharge the Leaf's battery.

And, importantly, the report underscores that as the grid gets cleaner over coming years, that reduced footprint is transmitted to a lower-yet impact when driving the Leaf (or any other electric car).

The group, according to its mission statement, rates vehicles "based on the scientific principles of ecological economics and calculated using scientific methods," rather than "subjective test-drive reviews."

A place for subjectivity?

We might gently argue that subjective assessments by experienced reviewers of a car's pros and cons--e.g. unintuitive controls, uncomfortable seats, numb steering, sensitivity to crosswinds--are useful information for potential buyers.

But we applaud efforts to provide more "objective" and "data-driven analysis" to help car shoppers make informed choices, and to "steer the consumer toward a purchase that best meets their needs, while also reflecting the values they live by."

How important is a car's lifetime carbon footprint to you? Does it factor into your buying decision, and if so, how much does it affect your purchase?

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