Reply #4: Energy efficiency isn't difficult to calculate

[IDemo]

If by "difficult" or "impossible", the experts actually mean - to present energy efficiency in a form the average citizen can wrap their mind around, they may be right. The commonly used MPGe, or miles per gallon equivalent, is pretty silly but not necessarily inaccurate.

Vehicle efficiency simply means how much energy does it take to move the vehicle a given unit of distance. Well-to-wheel efficiency includes the losses incurred in getting that energy to the rear (or front) wheel, but isn't included in mpg figures. My preference would be km/MJ, or kilometers per megajoule. Most American drivers would probably be much more comfortable with miles per kilowatt-hour, though.