Video: Ford Offers Explanation of Confusing MPGe

By · October 15, 2012

Ford MPGe

With the release of the official MPGe ratings for the C-MAX Energi, Ford released a video that simplifies the definition of MPGe.

With Ford's recent announcement that the C-MAX Energi was officially certified by the EPA with a rating of 108 MPG highway, 92 MPGe city and 100 MPGe combined, an explanation of these MPG-related terms was bound to come. A new Ford-produced video entitled, "Because You Asked...What is MPGe?" reduces the MPGe question to its simplest terms.

The use of MPGe has been somewhat controversial ever since the new era electric cars and plug-in hybrids—and the Society of Automotive Engineers, and the Enviromental Protection Agency started talking about the best efficiency metric for plug-in cars. More than two years ago, Mike Duoba, a research engineer at Argonne National Lab, warned not to dumb down EV efficiency with the use of MPGe. "Trying to boil [EV efficiency] information down to one number is only going to mislead people," he said. "There’s no magical way to turn electricity into gasoline.”

But MPGe is being used on window labels, and Ford's vehicles are scoring high on MPGe, so the company needs to make the high miles-per-gallon-equivalent numbers as meaningful and relevant as possible.

Unfortunately, the goofball approach to Ford's video plays into the notion of dumbing down EV efficiency, and we still question the usefulness of MPGe in comparing the efficiency of gas cars versus EVs. But maybe Ford's simplified explanation of MPGe is a start to re-opening the conversation.

Comments

· · 1 year ago

I calculated my mpg much different. I took Kwh cost per mile then compared that to gasoline cost ($3.50 at the time) and came up with I could drive 165 miles to the equavent cost of a gallon of gas. Of course if I lived in Cal I would need to use $4.50.
Hey, I maintanced my Leaf the other day, rotated the tires. LOL!

· Spec (not verified) · 1 year ago

MPGe is confusing since it is based on the 33.7KWH/gallon electricity energy equivalent of gasoline . . . something few people understand. However, it is useful because it does point out that EVs are naturally much more efficient than gas cars because of their MPGe numbers around 100 compared to around 30 for gas cars or 50 for hybrids.

And, by pure coincidence, it is kind of useful since the average cost of electricity is around the same price of gasoline right now. If you go with 11 cents/KWH and the EPA 33.7KWH/gallon then the electricity equivalent is ($0.11)*(33.7)= ~$3.71 per "gallon" of electricity. But as electricity and gasoline prices change, that current near equivalence will change. Specifically, the price of gasoline will continue going up whereas the price of electricity will remain largely stable.

· · 1 year ago

Spec, interesting but my electricity is $0.08 per KWH thanks to TVA and 33.7KWH/gallon is not consistent either. It does not take in consideration the efficiency of the auto being driven.

· Jesse Gurr (not verified) · 1 year ago

Red Leaf, that is nice that your electricity is so cheap. Here in California, its a little more pricy. A regular residential rate is based on which tier you are on during the month depending on how much electricity you use. More you use the higher your tier, with Tier 1 at 12 cents/kWh up to Tier 5 at 32 cents/kWh.

There is an electric vehicle plan where you get a separate meter for your car. Rates for that are between 22-28 cents/kWh on peak with 12 cents/kWh off peak.

If you decide to charge during peak hours(12pm - 9pm) you'll be paying $7.41 - $9.43 per "gallon of gas".

· VoltSkeptic (not verified) · 1 year ago

Red Leaf

Hopefully I didn't misinterpret what you meant, but 33.7 kWh/gallon is 'consistent', it is fixed (although gas containing ethanol might have a lower value but that isn't relevant) and independent of efficiency.

The efficiency of a car, basically how far one can drive on a unit of fuel (gallon or kWh), is a different calculation whose units are miles/gallon (mpg) or miles/kWh. A Yukon (~13 mpg) is less efficient than a Prius (~45 mpg), so the Prius will always go a lot further on the same amount of fuel . However if these cars' engines were burning electricity instead of gas they are going to go 13 and 45 miles, respectively, on 33.7kWh of electricity because that's how many kWh there is in a typical gallon of gas. A LEAF that is getting 3.3 mi/kWh will go 111mi using that same amount of energy, so in this case the LEAF efficiency, or MPGe, is 111. [Note that in order to be comparing apples to apples, the mi/kWh must be measured Wall-to-Wheels, e.g. what a meter before the EVSE (charger) says was put into the LEAF not Tank-to-Wheels which is what the LEAF dash instruments report].

Hopefully you meant that both efficiency and energy cost need to be considered when calculating the operational cost. A LEAF will always be more than twice as efficient as a Prius, but when it comes to cost of operation that efficiency can be offset by cost of the fuel. If gas prices go down ~60% or electricity goes up ~250%, then a LEAF will cost more than a Prius to drive. The question is which fuel cost will change more?

· Spec (not verified) · 1 year ago

@Red Leaf

33.7KWH/gallon is consistent. It is the efficiency of the automobiles that varies. And the efficiency of automobiles will pretty much always be lower than EVs because ICEs are just not as efficient as electric motors.

· Spec (not verified) · 1 year ago

@VoltSkeptic

Good explanation. But your question at the end is really really easy to answer. Both electricity and gas prices will go up over time but electricity prices will go up slowly where as gas prices will go up faster. Gas can only be made from oil which has limited supply and high world-wide demand. Electricity can be made from natural gas, coal, solar, wind nuclear, geothermal, hydropower, waves . . . even oil! With such a diverse energy supply, electricity prices will be very stable.

This is why electric cars will eventually gain popularity even if they are currently struggling.

· · 1 year ago

@Spec, That stability is predicated on public utility commissions not sticking it to the public, which seems pretty commonplace here in California. Anyone running more than a 100 watt light bulb between the hours of 8pm and 10pm is gouged by prima donna do-gooders here. Wait until they get their hands in the electric car rationing cookie jar.

· Callajero (not verified) · 1 year ago

I live in California and my PG&E off-peak rates for PEVs are about 9 Cents. A full charge costs me about a dollar (about 35 miles). Since my Volt also gets about 35MPG, when on 100% gas, my equivalent cost per gallon of electricty is $1/gallon. That's the bottom line! I don't understand why anyone would use the term kWh/gallon for comparison purposes, since all cars have widely different efficiencies. If a Hummer driver were to switch to a Volt, his equivalent cost would be about 30 cents per gallon as compared to the Hummer.

· Volume Van (not verified) · 1 year ago

Ideally we should use Miles / KWH (kilo watt hour) which is the unit of electricity.

· · 1 year ago

@ Callajero: You ask "why anyone would use the term kWh/gallon for comparison purposes, since all cars have widely different efficiencies" but kWh/gallon is not used for comparisons. It's used to convert an electrical efficiency number like 3.3 miles/kWh to a miles per gallon number which can be used for comparisons — to gas-burning vehicles. Yes, all cars have widely different efficiencies and that's what their widely different MPG (or MPGe) numbers reflect.

· Spec (not verified) · 1 year ago

@Michael ·

Put down the ideology and walk away. Go learn the facts. Enron & very poorly designed deregulation system screwed up the utility market, not the PUC. And plug in as many 100Watt bulbs as you want, I guarantee no one will do anything.

· Callajero (not verified) · 1 year ago

@Christopher C
Well, not sure if I agree. The battery in the Volt is fully charged at 11.5 kWh. I go 35 miles with that (equal to one gallon on the Volt gas engine). But the Hummer driver goes 10 miles with a gallon! So which number do you use in the denominator? RedLeaf above tells us it takes 33.7 kWh per gallon!! Which number is correct?

· Jesse Gurr (not verified) · 1 year ago

@Callajero

Wouldn't that be:
10 mi/gal * 1 gal/33.7kWh = 0.297 mi/kWh or
33.7 kWh/gal * 1 gal/10 mi = 3.37 kWh/mi

A LEAF as mentioned above, gets 3.3 mi/kWh. It is about 10x more efficient than the Hummer.

With that efficiency, the volt would go about 3.4 miles, (11.5 kWh / 3.37 kWh/mi = 3.4 miles), before the battery is depleted.

Oh, I thought the Volt had a 16 kWh battery.

· Callajero (not verified) · 1 year ago

@Jesse Gur
I guess my point was that I know for a fact that every time I charge up my Volt it goes over 35 miles before it runs out of juice. So, 11.5 kWh = 1 gallon. Not 33.7 kWh/gal. There is something wrong with the way it is calculated, unless I missed something.
btw Volt has a 16 kWh battery but only shows charging to about 11.5 kWh. Mine gets about 3.3 miles/kWh.

· Jesse Gurr (not verified) · 1 year ago

Well the point of all electric cars is that they are more efficient than gas cars Not sure where EPA got the 33.7 kWh/gal number, maybe its how much power a gas generator makes on 1 gallon of gas? Anyway, 1 gallon of gas is equal to 33.7 kWh of electricity, or maybe contains 33.7 kWh is more accurate.

I guess you can think of a gallon of gas as a battery that is fully charged at 33.7 kWh. If the Volt is charged to 11.5 kWh, then a gallon of gas contains 3x the energy that the Volt battery does. If you were to increase the Volt battery to 33.7 kWh, you should be able to go about 3x the distance you do now, which is 35 mile * 3 = 105 miles.

The math from my previous post more or less proves that the Leaf is 10x more efficient than the Hummer getting 10 mi/gal. If that's the case then the Leaf gets an equivalent 10 MPG * 10 = 100 MPG.

Hope that makes sense and I explained correctly.

· Jesse Gurr (not verified) · 1 year ago

Oh also, it is the gas engine gets 37 MPG, not the electric motor, it gets around 100 or so MPG equivalent. So just because you get 35 miles or so on battery only doesn't mean you get 35 MPG on all electric. Which is why electric motors are being pushed is because they can do more with the same amount of energy as a comparable gas engine.

· Objective (not verified) · 1 year ago

@Jesse Gurr: When a gallon of gas is burned, it yields 115,000 British Thermal Units of energy. It takes 33.7 kiloWatt-hours converted back to heat to yield 115,000 BTU's. That's where they get that "equivalency" number. What's misleading about that is that to convert energy from fuel to electricity requires an engine driven by the heat generated from that fuel, and the maximum conversion efficiency is limited by the laws of thermodynamics. While a complete 100% conversion from heat energy to electricity, which is impossible, would require only 3,412 BTU's per kWh, the current US generation fleet averages about 10,400 BTU's per kWh. Best available combined cycle gas turbine primary with heat recovery steam generator steam generators driving a steam turbine secondary are averaging somewhere around 8,500 BTU's per kWh. The electric motor is efficient at using electricity because that's the easy part. Making the electricity is the hard part.

A gallon of gas burned through a small Honda generator yields somewhere around 10 kWh.

You don't have to take my word on any of this though, it's all available information which can be looked up.

· Jesse Gurr (not verified) · 1 year ago

@Objective,
Thanks for the info, you learn something new everyday. Talking about BTU got me thinking of how I am charged for natural gas at my house. Its not BTU, but something called "Therms". Then I started looking for how many BTUs are in a Therm and found this.

http://www.physics.uci.edu/~silverma/units.html

It says that, there are 1.33 Therms/gal of gas. Which is what I was trying to find cuz I was curious about the natural gas cars and how they compared to regular cars in regards to dollars to fill up.

Lets see, the Civic natural gas holds about 8 gallons equivalent of natural gas. If I am charged about 65cents per Therm at home, from my gas bill, then: 1.33 Therms/gal * 8 gal = 10.64 Therms * $0.65/ Therm = $6.92. That is a pretty cheap fill up actually.
Looking at NatGas prices around me average around $2.30/gal equivalent. At that price it would take $18.40 to fill up. Way cheaper to fill up at home. Those same 8 gallons in a regular car would cost me 8 gal * $4.60/gal = $36.80

3410 BTU/kWh * 1 Therm/ 100K BTU = .0341 Therm/kWh or 29.3 kWh/Therm.
Interesting stuff.

· Spec (not verified) · 1 year ago

@Objective

Making electricity is the easy part. We can make electricity from natural gas, wind, solar, coal, nuclear, geothermal, hydropower, waves .. . even oil! Continuing to obtain large quantities of cheap oil . . . now THAT is hard.

And that is why moving to electric cars is a good goal . . . it allows the car to be completely independent from the underlying energy supply since you can make electricity from so many different energy sources!

· · 1 year ago

Wow I started some discussion. I am a Finance major working now in SCM and cannot hang with you guys on the engineering and chemistry. Need to get my daughter involved in this one. She is a Physics/Chemistry double major now in grad school.
I guess what I was poorly attempting to get too is that the Leaf is highly efficient with an electric motor that has special windings and magnets to create a highly efficient motor. I am not sure how that motor really stacks up to the other vehicles.
What I am saying is the Leaf was built to be pure electric vehicle not some conversion or hybrid or whatever. It was build for one purpose and to be really good at it.
Being a Finance major I look at cost to cost and drive out the equivalent mileage which is much higher. I really do not care about equivalent BTU. I care about what I spend right now for electricity to the mile and how that money will equate in MPG given the current cost of gas. To me the MPGe is understating my savings by about 50%.

· Callajero (not verified) · 1 year ago

I must be dense! One gallon of gas is equal to 11.5 kWh on my Volt because it can travel 35 miles on one gallon in gas mode and also about 35 miles on 11.5 kWh. The 33.7 kWh per mile would only work if I was driving vehicle that is 1/3 as efficient as my Volt. So why use the 33.7 kWh/gallon for general comparison?

· Jesse Gurr (not verified) · 1 year ago

@Callajero

Exactly! Your Volt is essentially 2 cars rolled into one. An electric car and a gasoline car. The electric car runs when the battery is charged and until the battery runs out, the gas engine doesn't come on. When the gas engine does come on, then you have a gas car. And the gas car is definitely 1/3 less efficient than the electric car.

Now the trick is to understand the efficiency numbers. I think I get what you are trying to ask now. So then let me put it to you a new way. But first we need to understand that the 33.7 kWh/gal number is a hard fact. A gallon of gas contains as much energy as a large 33.7 kWh battery. The problem is turning that energy into mechanical motion that is used to move the car forward.

Now we all know that electric motors are really efficient. They can turn electricity into motion fairly easily. So the electricity in the Volt's battery after unplugging from the wall is used effectively.

The gas engine is a different story. We all know that gas engines are really not efficient at all. This will tell you just how inefficient it is.

http://www.fueleconomy.gov/feg/atv.shtml

This basically tells us that a gas engine can be between 28 - 30% efficient in converting gas into energy. Plus parasitic losses like a/c, power steering, water pump for coolant, etc.... It can go into the mid 30% range for efficiency.

Now if it takes 11.5 kWh to go 35 miles and it takes 1 gallon of gas to go the same distance then the Volt engine is running at about 34% efficiency. Meaning the gas engine can only extract 11.5 kWh from 1 gallon of gas instead of a maximum 33.7 kWh . You can thank all the system losses from extracting energy from gasoline for that low efficiency.

Hope that helps.

· Objective (not verified) · 1 year ago

@Spec: Is there anything in particular you can tell us that might explain how it is you think you possess any true comprehension about energy, or what goes into the production of electricity? If so, do tell. I cannot imagine what it is.

· Bill Howland (not verified) · 1 year ago

@Objective.

You stated: "A gallon of gas burned through a small Honda generator yields somewhere around 10 kWh.

You don't have to take my word on any of this though, it's all available information which can be looked up."
.
A Honda Eu1000iA2 will run 3.8 hours @ 900 watts on .6 gal tank or 3.42 kwh, or 5.7 kwh per gallon. This is per the Honda Specification sheet for this small honda generator.

Alternatively it will run 8.3 hours @ 225 watts on a .6 gal tank or 1.867 kwh or 3.112 kwh per gallon.

This is an energy saving inverter generator, a standard part load generator would be worse. These numbers are 1/2 to less than 1/3 of what you stated.

I'm glad I didn't take your word for it.

· Objective (not verified) · 1 year ago

@Bill Howland: I'm glad you didn't either. I have already forgotten more than you're likely to ever learn about energy, and I only threw out a round number off the top of my head. Offering 10 kWhr per gallon was generous. The point is that it takes a lot of primary energy to make electricity. You just affirmed that it takes as much or even more than I asserted. Thanks.

Now, that finally being accepted, you can see that the energy required to propel an electric automobile is a multiple of the energy that the MPGe equivalent shell game would have the uninformed believe. By the smallest Honda suitcase generator running at best effieciency full load, you would burn 33.7 kWhr worth of fuel to put 5.7 kWhr to your car's battery charger. So great that the electric car is now going to go about 18 miles on that charge. Great.

But it's not that bad, because the US grid average efficiency is a lot closer to that 10 kWhr per "gallon" I threw out. Roughly 31% of the fuel consumed to drive our generation becomes output from the plants. About 93% of that makes it to the meter at your house, and we can stop there, because I believe the "miles per gallon electric" car rating is based on the power drawn by the charger as measured at that meter. So...

33.7 kWhr (fuel energy content) * 0.31 (generation factor) * 0.93 (distribution efficiency) = 9.7 kWhr net.

With that a Leaf is rated to go about 29 miles. Lot's of cars do better than that. The only advantage, being able to use any primary fuel for generation, is unfortunately badly offset by all of the battery limitations.

I'll go ahead and anticipate the next argument... how much upstream primary energy does it take to get the oil to the pump? Now that you've shown the motivation to look up and learn something, I wont bother offering my best recollection. Ah, what the hell... it's about a 15% to 20% loss in production, refining, and transportation. So a car getting say... 35 mpg is actually consuming from the well like it only gets about 28 mpg.

There you have it. Not much gain in energy consumed. Of course, depending on where and how you drive, the electric car might work out somehow, but until gas is up around $6 to 8$ per gallon, it's not going to compare well financially against pretty much anything Camry, Accord, or better.

· Objective (not verified) · 1 year ago

I never have really worked out how much primary energy is involved on average in getting the fuel to the generating stations, but that would work out showing that the electric car uses even more primary energy, but that may very well be something only like 3% loss or so, and we've already shown that the major coverup is in the generation losses, so I leave that to somebody else to dig up.

Hey Bill... you going to keep this up?

It's never to late to get an education, you know.

· Callajero (not verified) · 1 year ago

While you are at it why do you count the total energy used from "well-to-wheels" including the energy it takes to do exploratory drilling! I am sure your results will be very different.

· Objective (not verified) · 1 year ago

What I'm saying is, I'll bet it doesn't take too much energy to do some exploratory drilling in your back yard, eh?

· Bill Howland (not verified) · 1 year ago

@Objective

You've yet to teach me anything. And .93 distribution efficiency is too high, in general. Congratulations on being the most pompous person on PluginCars.com. You especially attack people who are up to your challenge. Strong volume does not compensate for a weak argument, The only anticipatory comment I'm going to make is to wait for you to say something interestingly intelligent.... But I think that's a bit part of your game.. Please reread the first sentence in this paragraph. Then, think about the times you've just been plain WRONG. So who is teaching whom man? And I will wait in silence.

· Callajero (not verified) · 1 year ago

OK. This is getting too nasty for me. I am going to go out and drive my Volt to relax!

· Bill Howland (not verified) · 1 year ago

@Callajero

I don't know what year Volt you have but the 2011 I have has default Bose stereo and DVD player... I watched some old Columbo TV shows in my Volt, and it is INDEED very relaxing!! The Picture is a bit fuzzy, but the sound is better than I've ever heard. The Studio must have used the Master tapes to record the soundtracks on the Columbo DVD's. Anyway its extremely relaxing, but you can't drive and see the DVD at the same time due to their predetermined restrictions.

· Bill Howland (not verified) · 1 year ago

Note to Editor:

If you have a method of reading "OBJECTIVE" 's posts, please see if he is deemed too LOW BROW a poster and is denegrating Plugincars.com Wholesome Americana nature. The references to Feces are particularly disgusting for a classy blog place such as this.

Sincerely,

Bill Howland

· Objective (not verified) · 1 year ago

Thanks again for acknowledging that... 0.93 is the generous rounding up of the best available number. I could have offered 0.92 and that would have been pretty close, too.

Bill, the reason you don't know shit is because you want to remain ignorant.

· Objective (not verified) · 1 year ago

@the editor: The premise of your whole site is a farce, and when you edit peoples comments without even indicating that you have, you are being dishonest. That's what makes this site nothing but propoganda, designed to fool those it can into believing what's not true. But, you profit from it , so you have to keep doing it, but make believe there is some worthy reason. The truth though, is that you lie to make money. What does that say about you?

@readers: Here's one of the removed posts:

@Callawhatever: I did, it's in that 15 to 20%. Why don't you do it yourself and check me on that. Bill discovered an error in the Honda generator number. I'd build him a monument for that if I could, but [this word edited out by the spineless moderates to protect the mentally week (that's you, Bill)] doesn't stack high enough to do him justice.

· Objective (not verified) · 1 year ago

@moderator: Please fix my spelling on the previous post. For the word "moderates," it should have been "moderator."

· Bill Howland (not verified) · 1 year ago

@objective

I bet you're all of 14 years old and because you know a very few facts you think you know everything there is to know, and no one else knows anything, .92 is still much too high.

Here's a question to see if you know anything at all. I'm in the downtown area of any major city on their many decades old Network System. I have a single element 2 wire water heater running on the highest voltage the NS can produce. Assume a short, thick wire run between the serving utility and the heater,. What is the power factor and sense on each phase of the transformer bank supplying only this water heater with other loads shut off?

· Objective (not verified) · 1 year ago

@Bill Howland: I thought I told you to go [] yourself? I thought you said you were done?

No matter. The ~0.92 is a simple calculation from the difference in the total power metered into the grid from the generating stations, and the power metered off of the grid at the loads. You can look that up, too. And if my sources provided too high an efficiency factor, that only shows that electric cars are using that much more energy.

You, and just about every other EV advocate on this website and others, are emotionally vested in the success of something so badly that you can't see your nose for your face. Here's how to fix that, unzip your zipper an peek into the mirror, because you've got your head so far up your rectum that's about the only way you're going to see it.

I've operated both naval nuclear reactors, and commercial power reactors, and I've watched engineers like you get dropped from the program without a license... because some of them just can't use their head. You'd be in that category.

Now, like I told you before... go [] yourself.

· Bill Howland (not verified) · 1 year ago

@objective

I've never seen such a silly person on here as you... After this post you wont hear me responding.. I still think you are 14 years old, and are lying about everything else. Your dad might have done the things you've mentioned, but its doubtful you will ever learn as much as him. I gave you a simple problem to solve, and you don't know how to even begin to answer it. 'Nuff said.

· Objective (not verified) · 1 year ago

How much public money should be spent on a gamble that I am 14?

You might as well advocate as much as for the electric cars you love.

Your conclusions in each case are based only on a guess made in a fit of emotion.

Lesson over. You failed.

· Fred (not verified) · 1 year ago

i used the fuel cost calculator to check the free truck rate
and it gave me the exact rate details.so you guys can check it..

· William (not verified) · 1 year ago

i used the Distance calculator to check the free truck rate
and it gave me the exact rate details.so you guys can check it..

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