Vehicle of the Future

EV enthusiast and activist

Posts Tagged ‘economy


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There’s all this talk about MPGe (Miles per Gallon equivalent), what it really means, and how it’s calculated. The truth is, there’s no good way to compare EVs to internal combustion through MPGe. If you really want to compare in any meaningful manor check out the miles per $ metric.

That said, there’s really three ways to calculate MPGe. I call it the three E’s, Efficiency, Emissions, and Economy. It’s really about comparing some measurable characteristic of an EV and cross multiply to get rid of the unwanted units.

The following calculations are based on June 15th data from an earlier blog post.

MPGe Efficiency

This is how the EPA, auto companies, and Big Oil want you to calculate MPGe. Basically, a gallon of gasoline can be burned and rendered useful as kWhs of electricity, thus comparable to an EV that uses kWh of electricity. The conversion is: 33.7 kWh electricity per gallon of gasoline.

So, my Leaf which gets:

(3.36 mi/kWh) X (33.7 kWh/gallon) = 113 MPGe

MPGe Emissions

Using the calculator at AfterOil EV, one may compare MPGe by total CO2 emissions from generation to wheels by emissions ratio. I used 50.3 miles @ 35MPG, comparable vehicle to my Leaf, and a very liberal estimation at that.

(31.8 lbs CO2 Ave Car) / (14.09 lbs CO2 Leaf) = 2.25 ratio (times fewer emissions)

(2.25) X (35 MPG) = 79 MPGe

MPGe Economy

This is how I’d like to measure MPGe. After all, why compare vehicles using a metric of economy (MPG) unless one does so using units of economy.

(3.36 mi/kWh) / ($0.12/kWh) = 28 mi/$

(28 mi/$) X ($3.999/gallon) = 112 MPGe


Written by devinserpa

June 28, 2011 at 1:18 pm

112 MPGe Total System Economy

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Daily Miles

Daily kWh

My average daily commute taken on June 15th was 50.3 miles. That night a full charge was 14.97 kWh.

(50.3 mi) / (14.97 kWh) = 3.36 mi/kWh

So my car is getting approximately 3.36 miles per kWh used including charging losses. On Tier 1 with PG&E I’m paying $0.12/kWh.

(3.36 mi/kWh) / ($0.12/kWh) = 28 mi/$

I’m getting 28 miles per dollar total system economy with my Leaf.

(28 mi/$) * ($3.999/gal) = 111.97 MPGe

The Leaf gets 112 MPGe

This is based on ‘wall’ to wheel economy.

Written by devinserpa

June 16, 2011 at 2:02 pm

136 MPGe ‘Tank’ to Wheel Economy

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My car is getting approximately 4.1 miles per kWh as reported by my Leaf. On Tier 1 with PG&E I’m paying $0.12/kWh.

(4.1 mi/kWh) / ($0.12/kWh) = 34.167 mi/$

I’m getting 34 miles per dollar with my Leaf. Compare that to 7.5 mi/$ with my Civic. Now,

(34.167 mi/$) * ($3.999/gal) = 136.63 MPGe

The Leaf gets 136 MPGe, that’s miles per gallon equivalent.

This is based on ‘tank’ to wheel economy.

Written by devinserpa

June 12, 2011 at 1:03 am

Most Economical / MP$

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The only way to comprehend transportation economics is to use a common metric. Miles per gallon is fine for comparing efficiency, but only for like vehicles.

Try comparing a MPG for gas and a MPG for diesel. There’s different costs per gallon for the two fuel types which makes true comparison limited.

Then there’s dollars for kg, for hydrogen fuel cell vehicles versus dollars per kWh for electric vehicles. This compares raw energy costs but not consumption.

A Miles per Dollar metric is needed to compare all the different engine types and fuel types. EVs are the most economical at over 18 mp$ at conservative numbers. Compared to 6 mp$ for a gasoline vehicle, EVs are over three times as economical.

Written by devinserpa

May 24, 2011 at 5:56 am

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