Figuring 25% general efficiency of the ICE power sources, and 80% efficiency of electric motors, about 11,000 watt-hours of electricity will do what one gallon of gasoline does.
This is useful when considering conversions and such. Motorcycle conversions for instance maybe average 50 mpg. Well 11,000 watt hours of stored electricity will get you that same 50 miles. Car conversions, same deal, one gallon will get you what 11,000 watt-hours will get you.