Electric vehicles would be even cleaner if utilities switched away from coal and natural gas and leaned more heavily on low-emissions sources like solar, wind or nuclear power.

That combination could have a powerful impact: One recent study by Carnegie Mellon University found that if America’s grid was close to emissions-free, and if about 84 percent of all vehicle travel was electrified, transportation emissions from light-duty vehicles would fall by 90 percent. (The decline in emissions could be even faster and larger, the study found, if policymakers took actions to reduce reliance on driving, such as expanding public transit or encouraging biking and walking.)

“The grid is getting cleaner over time, but it’s still not at zero emissions,” said Constantine Samaras, an associate professor of civil and environmental engineering at Carnegie Mellon University and a co-author of the paper. “If we want to fully decarbonize transportation, we need to do everything, and do it at full speed: fewer vehicle miles traveled, electrify nearly the entire passenger fleet, and clean up power plants.”
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