New Metric For Car Efficiency: Miles Per Dollar Spent On Energy?

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It's downright confusing trying to calculate how much it costs to run green cars, whether it's a 50-mpg Toyota Prius or a highly efficient electric car like the 124-MPGe BMW i3.

One of the problems is how to use different efficiency ratings for various powertrains--gasoline, hybrid, electric--to calculate actual cost.

As it turns out, the AfterOilEV blog has suggested a metric that covers all of these options: How many miles do you get from different cars when you buy $1.00 worth of energy?

DON'T MISS: One Owner's Chevy Volt Running Cost: 2 Cents Per Mile (Jan 2013)

On new-car window stickers, the U.S. Environmental Protection Agency uses miles per gallon for cars with engines, and MPGe (miles per gallon equivalent) for plug-in cars.

The MPGe measurement is the distance a car can travel under electric power on the same amount of energy that's contained in 1 gallon of gasoline.

The ratings underscore the point that electric cars are far more efficient in using energy than gasoline or diesel vehicles.

2016 Chevrolet Volt

2016 Chevrolet Volt

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While the 50-mpg Prius is the most efficient car sold in the U.S. without a plug, the BMW i3 comes in at 2.5 times as efficient: It's rated at 124 MPGe. No gas car can touch that.

The challenge comes in comparing the running cost of a hybrid to that of an electric car.

And it's exacerbated by the fact that a majority of U.S. residents can't answer this question: "So how much do you pay for 1 kilowatt-hour of home electricity?"

ALSO SEE: Electric-Car Efficiency: Forget MPGe, It Should Be Miles/kWh (Mar 2013)

The AfterOilEV "Mp$" metric page lets you specify the prices of different types of energy on which a vehicle can run.

It includes not only gasoline, diesel, and electricity, but also biodiesel, compressed natural gas, pure ethanol, E85, and even E20, E30, and hydrogen.

A miles-per-gallon rating can be entered for gasoline vehicles (not diesels, only), and default prices can be changed, where you know current local pricing.

Gasoline, for instance, is presently under $2.00 a gallon in many regions of North America, increasing its cost advantage over diesel fuel.

Meanwhile, the average electric rate is about 12 cents/kWh--but standard rates can vary from 3 to 25 cents per kWh.

On the other hand, energy costs have changed since the page was last updated in May 2011.

MORE: Energy Department Launches 'eGallon' To Explain Electric-Car Cost, Efficiency (Jun 2013)

Nevertheless, it's a very clever way to look easily at the distance you can drive for a dollar across different vehicles with various alternative powertrains.

HINT: Electricity wins most of the time.

[hat tip: Devin Serpa]

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