The 2013 Ford Fusion, that was recently named Green Car of the Year, gives a nod to the Fusion Energi plug-in hybrid, rated by the US Environmental Protection Agency at 108 MPGe, making it arguably America’s most fuel-efficient vehicle.

Of course this information is a little confusing with the “e” attached to the MPG number, as you ponder  “What the heck does that really mean?”

Well the EPA has rated a gallon of petrol as equivalent to 33.7-kilowatt hours of electricity. The problem is it’s an energy equivalent that bears no relation to dollars OR sense.

Does the 33.7-kilowatt hours cost the same as a gallon of gasoline? Actually it costs much less in most places, but what it costs exactly is generally undefined. The power company could tell you, but when you charge your car determines how much the electricity costs.

You can fill your 14-gallon petrol tank, spending about $40, in about 5 minutes. Your plug-in car can go say 50 to 300 miles on a charge, but that takes from four to eight hours.

This is where the EPA’s equivalent breaks down. If time is money, then money is time. So what does 108-MPGe tell us, except that the EPA thinks maybe you should buy one?

What is needed is a way to compare cars that use petrol, diesel, natural gas or electricity in a way that equates to both these concepts! This would free people from hours of research without really understanding how to compare these variables in application to a particular lifestyle or region.

One fact that does make sense is the EPA rating that the Ford Fusion Energi Plug-in could potentially save customers $6,850 on fuel over five years. Of course, this is another place where the EPA ratings are not really useful. When you see a sticker with an annual fuel cost estimate, does it really mean much? If you fit some national average, drive a predictable amount, live in a place where petrol is at a median price and think of yourself as average, maybe it works.

Getting back to Ford, none of the above is their responsibility – the Fusion Energi marks their fifth electrified vehicle launched during the last year. Ford is accelerating investment in hybrid technology and it’s paying off in sales with November racking up the highest monthly hybrid sales month yet.

Despite the currently low price of petrol, Ford is now ranked first in fuel economy and customer satisfaction by J.D. Power, replacing Toyota as the efficiency leader in every category the two compete.

“The Fusion Energi plug-in hybrid is the exclamation point for Ford’s transformed lineup of fuel-efficiency leaders that now beats Toyota across the board,” said Raj Nair, group vice president, Global Product Development.

The addition of Fusion Energi gives customers yet another Ford option when shopping for an electrified vehicle, added to the Focus Electric, Fusion Hybrid, C-MAX Hybrid and C-MAX Energi.