Miles Per Gallon Equivalent by Four Different Methods

[04_Sentra]

Originally Posted by Old Mechanic

I don't know about the rest of you, as to how successful you have been in converting others to efficient driving techniques, but personally I find the ignorance astounding and the attitude that I am some kind of obsessed, semi nutcase, because I focus on efficiency.

I have to second that. I'm generally considered a lunatic by my coworkers because instead of spending my money on ski boats and lux cars I spend it on making my house more efficient to drive down electricity use, voluntarily pay a higher electricity rate so that all my electricity comes from renewables, take public transportation to reduce miles driven, and actively seek out locally grown groceries.

Conversation typically goes like this:
Him: Hybrids don't make any sense because you never make up the cost premium in saved gas, everyone knows that.
Me: Don't you drive a $50k SUV that gets 15mpg.
Him: Yes.
Me: So then you don't actually believe in this economic model of car buying where the car has to somehow pay for itself. Otherwise you'd own a Geo Metro.
(long pause while that sinks in)
Him: You're a hippie.

These conversations typically end with me being called a greenie, treehugger, or hippie.

[RobertSmalls]

Originally Posted by 04_Sentra

Personally, I don't like any of the methods of calculating mpge.

Life Cycle Energy Equivalence - Unfairly compared Well to Wheels for EV to Tank to Wheels for ICE.
CO2 Equivalence - Makes an assumption on where I get my electricity and it's CO2 content.
Cost Equivalence - Makes an assumption on how much I pay for electricity.
Direct BTU Equivalence - Gives unrealistic expectations on the range and cost of operation for EVs.

What I need to know is capacity of battery pack in kWh, and "fuel economy" in wh/mi, and I can figure the rest out.

I don't like the term "mpge", because wh/mi can not be made equivalent to mpg. Certainly not universally. Still, you can do a weighted average of the above methods, tailored to your specific situation and values. You can also make some reasonable assumptions about people's values, and you'll come up with a figure that's about half of the direct BTU mpge figure.

Let me stand up for the first two methods.

Life cycle energy equivalence: I have presented well-to-wheels data for gasoline (not tank-to-wheels), and well-to-plug data for electric, so you must measure power consumed by the charger, not by the inverter as reported on the dashboard.
CO2 equivalence: Considering that electricity is fungible, and we're all on the same grid, grid average figures are appropriate for estimating the impact of mass adoption of EV's.

[04_Sentra]

I don't have any disagreement with your W2W analysis of EV vs ICE. The comment on mpge being Life cycle energy is unfair to EVs was because mpg is always tank to wheels. So if mpge is Life cycle energy then it isn't really "equivalent" to mpg as the name suggests.

[roflwaffle]

Originally Posted by RobertSmalls

CO2 equivalence: Considering that electricity is fungible, and we're all on the same grid, grid average figures are appropriate for estimating the impact of mass adoption of EV's.

Well, kinda. Californiastan is at ~300-450grams of carbon per kWh depending on whether you're looking at the electricity produced in state or consumed in state. The U.S. average is ~600g/kWh and some places are as high as ~1000g/kWh.

[dcb]

Someone explain to me why mpge is even necessary?
What is so terrible about listing mpg and kw/mile separately?
Mpge is a solution in search of a problem, while making new problems in the process.

[RobertSmalls]

Originally Posted by 04_Sentra

I don't have any disagreement with your W2W analysis of EV vs ICE. The comment on mpge being Life cycle energy is unfair to EVs was because mpg is always tank to wheels. So if mpge is Life cycle energy then it isn't really "equivalent" to mpg as the name suggests.

Unless you apply a 17% bonus to the mpge conversion factor to account for this fact.

[RobertSmalls]

Originally Posted by roflwaffle

Well, kinda. Californiastan is at ~300-450grams of carbon per kWh depending on whether you're looking at the electricity produced in state or consumed in state. The U.S. average is ~600g/kWh and some places are as high as ~1000g/kWh.

I live near a hydro plant. But if I conserve electricity, the hydro plant can sell its CO2-neutral electricity to someone in New Jersey who would otherwise be buying from a coal-fired power plant.

[NeilBlanchard]

Matt, did you read this?

http://www.pluginamerica.org/images/...onsSummary.pdf

From page 3:

Greenhouse gases (GHGs):

...

EVs reduce CO2 by 11%-100% compared with ICEs and by 24%-65% compared with
HEVs, and significantly reduce all other greenhouse gas emissions, using the U.S. grid
mix. If all U.S. cars were EVs, we’d reduce global warming emissions even on today’s
mostly coal grid. Using electricity strictly from coal, EVs still would reduce CO2 by
0%-59% compared with ICEs (two analyses found 0% change; seven others found
reductions of 17%-59%) and might produce 30%-49% more CO2 than HEVs (based on
only two analyses) on today’s grid. On the other hand, if electricity comes from solar or
wind power, EVs eliminate all emissions. Using natural gas to make electricity,
emissions fall in between those from coal and renewable power.

[TomEV]

Originally Posted by dcb

Someone explain to me why mpge is even necessary?
What is so terrible about listing mpg and kw/mile separately?
Mpge is a solution in search of a problem, while making new problems in the process.

IMHO, for a BEV such as a Leaf, or an iMiEV, or my Citicar, wh/mi is an appropriate measurement. I include my wh/mi in my 'garage' posts, but the system here is geared towards fossil fueled vehicles, thus the odd 159 MPG number by my vehicle. The MPGe rating for my EV is somewhat disingenuous. Perhaps there will be a site change here in the future to choose between wh/mi and MPG.

'Combined mileage' numbers, such as the 129 MPG number used by an auto magazine for a Volt test, and a 80 MPG number used in a plug-in Prius test, are very misleading and should not be used - Does a driver only drive 5 miles a day? Does a driver commute 200 miles a day? What happens to the combined mileage number when a plug-in hybrid can't be plugged in for some part of a particular trip?

The MPGe rating comes into place with plug-in hybrids. Comparing a Volt with a Plug-in Prius (both are basically plug-in hybrids; neither is an EV) an MPGe number would have more significance - perhaps a depleted-pack MPG over electric-only wh/mi.

As an example, a Volt may get an MPGe number along the lines of 40/266 (MPG depleted over wh/mi) and a plug-in Prius may get 50/220. These numbers are speculative, but close based on some auto magazine tests.

For an efficient plug-in hybrid, one would look for a high first number and a low second number.

[04_Sentra]

Originally Posted by dcb

Someone explain to me why mpge is even necessary?
What is so terrible about listing mpg and kw/mile separately?
Mpge is a solution in search of a problem, while making new problems in the process.

Its not necessary. It looks like most/all of the people on this list don't like mpge, but mpg is very familiar and its what the average car buyer understands. I suspect that Big Brother will saddle EVs with an mpge rating instead of a more accurate Whr/mi and somewhere in Washington there is an oil industry lobbiest pushing for the mpge calculation to put EVs in the worst possible light.