Video: Ford Offers Explanation of Confusing MPGe

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.

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".

@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.

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

@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

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.

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: 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.

@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!

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?

@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: 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.

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

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

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.

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.

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

@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.

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.