Governors' Wind Energy Coalition

China is on track to seriously beef up its electric vehicle fleet — but is that really better for the environment?

Coal still accounts for much of the country’s electricity production. Charging electric batteries could generate more carbon dioxide than combustion engines do. Researchers are seeking a better understanding of exactly how, when and where electric cars are charged in order to determine whether electric motors pollute less than gas engines.

“EVs may just be moving air pollution from one part of the country to another,” said Scott Kennedy of the Center for Strategic and International Studies.

A study published earlier this month in Nature Energy found that charging EVs during the day or in “fast mode” gives them a significantly higher carbon footprint. “If people were incentivized to wait until evening and charge their vehicles in the slow-charge mode, which takes hours, the power load could take advantage of wind energy available during off-peak hours,” said study co-author Chris Nielsen of Harvard University.

Another study found that cars that get better than 40 mpg were less polluting than EVs because of China’s reliance on coal. But the share of power that China gets from coal is expected to drop to less than 50 percent by 2040, down from 72 percent in 2015, according to the Energy Information Administration.