eQ factor

The ratio of the cost of a gallon of gasoline to the cost of an equivalent amount of electrical energy, based on a gallon of gasoline having 115,000 BTUs which is equivalent to 33.7 kilowatt-hours. The eQ factor is used to determine how many miles one gets in an electric vehicle for the same dollars spent on a gallon of gasoline. This is different than MPGe which does not account for price differences between gasoline and electricity. To figure the eQ factor, first calculate the the cost of an equivalent amount of electrical energy in your locale by multiplying 33.7 KwH by the cost per kilowatt-hour of electricity (including delivery charges, if any). Call that the "Cost of a Gallon of Electricity". Take the cost of a gallon of gasoline in your locale, and divide it by the "Cost of a Gallon of Electricity" to get the eQ factor. The eQ factor changes depending on the prices of gasoline and electricity in a particular location on any given day.

To figure out how economical that electric car really is for you, multiply the MPGe rating from the EPA by the eQ factor to see how many miles you'll get for the same dollars you spend on a gallon of gasoline.