What is MPGe
As the figure of merit for fuel economy, the Progressive Insurance Automotive X PRIZE is using MPGe (miles per gallon energy equivalent), defined as:
MPGe = (miles driven) / [(total energy of all fuels consumed)/(energy of one gallon of gasoline)])
MPGe is a simple, well-defined measure of overall vehicle efficiency. MPGe is easy to explain, accounts in a neutral manner for any combination of fuels, and reduces to the familiar MPG in the case of gasoline fuel only.
To make it easier to understand (and get some intuition about) MPGe, the Progressive Insurance Automotive X PRIZE developed a spreadsheet available here. It includes three simple calculators:
(1) Enter the distance driven and the amounts of all fuels consumed – result is MPGe. The formula for this calculation is the one given above.
(2) For the special case of gasoline-electric PHEVs, enter the gasoline usage (MPG gasoline) and electricity usage (watt-hours per mile) – result is MPGe.
(3) For the case of any plug-in vehicle, enter the charging time and the charging efficiency – result, for three different electric circuit types, is the total energy added to the battery, expressed both as kWh and as (energy-equivalent) gallons of gasoline.
This is a hard time for the automotive industry. But it’s also an exciting time of change and innovation. Consumers will soon have a variety of energy efficient and environmentally friendly vehicle choices as diverse technologies and alternative fuels come to market. This diversity will make it harder to evaluate and compare vehicles, and how best to do so is a difficult question. MPGe is not the entire answer, as it must be presented in the context of driving style, frequency, and distance.
