A new study places a dollar-based price tag on the environmental benefits of electric vehicles in terms of avoided greenhouse gas pollution, and the answer may surprise both clean-car enthusiasts and skeptics.

In the western United States, where electricity is generated from a relatively clean mix of fuels and methods, replacing a mid-sized conventional car with a plug-in electric vehicle can avoid pollution damages equivalent to $425, according to the soon-to-be published study from three researchers at the University of California, Davis.

That estimate of pollution benefits is below government subsidies attached to all-electric vehicle sales, including a $7,500 federal tax credit, California’s $2,500 rebate and a variety of state-by-state perks such as reduced vehicle registration fees and unrestricted access to car-pool lanes.

“There is still a very widespread common wisdom that electric vehicles are carbon-free or really good for the climate,” said David Rapson, an economic professor at UC Davis and one author of the study. “That is only partially true, and it really depends on where you are.”


The analysis by Rapson, university colleague Alissa Kendall and graduate student James Archsmith, looks at what would happen if an average household in the U.S. were to buy a new mid-sized electric vehicle instead of a comparable gasoline-drive car.

Avoided pollution benefits were calculated under the White House’s social cost of carbon price, a tool that helps federal agencies decide on carbon-reducing strategies.

Across portions of the Midwest, the move to an electric vehicle results in more carbon pollution -- not less.

That conclusion is based in large part on performance limitations of electric vehicles during cold weather, when batteries lose efficiency and can’t rely on excess engine heat from fuel combustion to warm the driving cabin.


At the same time, increased electricity demands in certain states are likely to be filled by high-polluting sources of electricity, in particular from coal-fired power plants, the study found.

Consideration was given to emission during the entire life cycle of vehicles, from “cradle to junkyard,” including the manufacturing process.

For internal combustion vehicles, that includes the pollution involved in extracting crude oil from the ground and refining it into gasoline.

The study admittedly left out other health and societal benefits linked to electric vehicles, such as protecting certain populations from highway-related soot and smog, or decreasing U.S. dependence on foreign oil. It does not parse the possible benefits of hybrid vehicles.


Brett Williams, a senior project manager at the Center for Sustainable Energy that administers California’s clean-vehicle rebates, said subsidies for advanced technologies including electric cars often are designed to overcome difficult initial social and economic barriers.

Electric vehicles, he pointed out, are expected to pay increasing environmental dividends as the power grid integrates more renewable energy and phases out dirtier sources of energy.

On that point, the UC Davis study provided mixed forecasts.

In western states such as California, the greenhouse-gas benefits per electric vehicle are expected to reach $2,380 by 2040.


In cold-weather, coal-reliant states, the benefits of electric vehicles will depend on the evolution of the power grid in terms of renewable energy, fossil fuels and nuclear reactors. Internal combustion vehicles still could hold environmental advantage in 2040, under some scenarios foreseen by the Energy Information Administration.

Rapson said the study has undergone anonymous peer review ahead of publication in a special edition of Research and Transportation Economics. It was circulated publicly this month by the Berkeley-based Energy Institute at Haas.