The study, performed for the U.S. Department of Energy's Pacific Northwest National Laboratory in Richland, Wash., indicates replacing vehicles solely powered by gasoline engines with hybrids powered by off-peak electricity could improve air quality by using existing infrastructure more efficiently, the laboratory said in a news release Monday.

Batteries for plug-in hybrid electric vehicles could store enough energy to meet the nation's 33-mile average commute, researchers said. If drivers charged vehicles overnight when demand for electricity is low, most regions of the country would have plenty of off-peak generation, transmission and distribution capacity to handle that region's hybrid vehicles.

"Since gasoline consumption accounts for 73 percent of imported oil, it is intriguing to think of the national security benefits if our vehicles switched from oil to electrons," lab energy researcher Rob Pratt said.

The extra electricity needed to power the vehicles would come from coal-fired and natural gas-fired plants, researchers said. While these power plants emit greenhouse gases, overall levels would drop because electricity is more efficient to move a vehicle one mile than producing and burning gasoline.