Since the days of Thomas Edison, finding a way to effectively store electricity has been one of the “Holy Grails” for power companies.

While it won’t be an overnight revolution for electricity, eventually plug-in electric cars and trucks will be a step toward the elusive goal, said Ted Craver, chief executive officer of Edison International.

Edison International is the parent of Southern California Edison (SCE), which is the biggest utilty in the United States in terms of power delivered to customers.

 ”They are effectively storage units on wheels,” Craver said of electric cars and trucks.

Vehicles batteries charged during off-peak periods could feed power back to the grid during periods of peak demand, said Craver in a telephone interview on Thursday.