mpg vs. mpge

[nosuchthing]

So, I'm reading this article...

http://insideevs.com/top-10-fuel-sippers-epa-ratings/" onclick="window.open(this.href);return false;

...and have always wondered about this mpge concept for BEVs. There is this hard number where the mpge calculation comes from: 33.7 kWh = 1 gal. of gasoline. Seriously? Is it for Pennsylvania or sun-powered California? Some sort of average? Where did this number come from?

I'm running on 100% green juice (i.e. deep green PG&E/MCE plan). As far as I'm concerned, my mpge is infinity.

What gives?

 

[GetOffYourGas]

You are thinking about it wrong. A kWh is a unit of energy. They are saying that 1 gallon of gasoline contains 33.7kWh worth of energy. It has nothing to do with where your electricity comes from.

 

[nosuchthing]

So it's all about average energy per miles efficiency. I get it.

 

[DNAinaGoodWay]

Humans seem to have a need to relate new things to old things, thus, horsepower. Might be more relevant to use $/mile, but that would factor in what you pay for relative sources of energy. It's fun to tell people that you get over 100 mpg, e. Makes it relatable to them.

 

[Levenkay]

Because most people that seek to compare "mileage ratings" among different vehicles are really trying to get a handle on operating cost, I think that it's far better to compute "miles per dollar" for each of the vehicles being compared. I tell people that my LEAF gets 40 mi/$, which isn't exactly correct, but it's pretty close. Multiplying that by the $/gal price of fuel on any given day gets you to a more relevant way of determining "mpge".

 

[Graffi]

You are thinking about it wrong. A kWh is a unit of energy. They are saying that 1 gallon of gasoline contains 33.7kWh worth of energy. It has nothing to do with where your electricity comes from.

So if one gallon of gas contains 33.7kwh worth of energy, then our Leaf, which gives us something greater than 4 miles/kwh, will give us 4x33.7=134.8 miles. So each night when we recharge our Leaf we are using just over 1/2 gallon of gas equivalent electricity.

Since my ICE get anywhere from 25 to 32 mpg, I can go about 68 miles in the leaf compared to about 14 miles in the ICE.

I still prefer to compare cost per mile as both gas prices and electricity cost vary with the area of the country (or world) each of us live in.

Thanks for this info. Interesting.

 

[nosuchthing]

I usually tell everyone that I drive on $1 or less per gallon gas. That is the easiest way to quickly explain the savings to non-electronauts.

Then I quickly add, no matter what gallon of gas costs, 3 or 5 bucks, I pay 1 dollar (or less). That's roughly the cost of juice, 19-21 cents per kWh (juice + transmission) at the average of 4 m/kWh.

 

[Nubo]

It's a bit silly to evaluate an EV's performance in terms of *gallons* of anything. We don' need no steenkin' gallons! :lol:

The reluctance to use basic electrical units in instrumentation and advertising is really weird. Car executives seem to think we'll recoil in horror from volts, amps, watts.... EVs will really have arrived when Joe Sixpack can rattle off specs like M/kWH, and 100kW motors.

 

[dgpcolorado]

It's a bit silly to evaluate an EV's performance in terms of *gallons* of anything. We don' need no steenkin' gallons! :lol: ...

Yes:

[Thanks to FalconFour for making the decal.]

 

[seascribe]

Absolutely! Cost in $ for distance driven is the only sensible way to compare ICE and BEV.

 

[GetOffYourGas]

Absolutely! Cost in $ for distance driven is the only sensible way to compare ICE and BEV.

For the consumer, I agree. The trouble is, this is not a straightforward comparison. The EPA sticker does provide this information, though, using nationwide averages and clearly stating their assumptions.