Electric vehicles already deliver much less pollution over their lifetime than gas-powered vehicles.

There’s a simple way to reduce EV emissions even further: with smart charging.

RMI and WattTime found that when EVs are optimized with smart charging to align with times of low emissions on the electricity grid, they further reduce emissions by an additional 2–8 percent and even become a grid resource.

The report More EVs, Fewer Emissions finds two key factors that affect the amount of emissions saved from optimized EV smart charging: the local grid mix and charger speed.

Even on dirtier grids, optimized charging can still play a role in reducing emissions and their associated pollution. This report digs into the differences in six regions in the United States and offers strategies to optimize EV charging everywhere.

For example, the maps below show the carbon savings achieved across the United States when charging during the day versus night depending on the region’s predominant fuel source.