Compare electricity costs and gasoline costs per unit energy

A gallon of gasoline has about 125,000 Btu.
1 kilowatt-hour of electricity = 3,413 Btu.
http://www.jwiwood.com/faq/conversion.html

So a gallon of gasoline contains 36.6 kwh of energy.

Gasoline costs about $3.50/gallon.
And 36.6 kwh costs about $2.38.