Comparing Energy Costs per Mile for Electric and Gasoline Vehicles

[kristopher]

Comparing Energy Costs per Mile for Electric and Gasoline Vehicles

The fuel cost of driving an electric vehicle depends on the cost of electricity per kilowatt-hour (kWh) and the energy efficiency of the vehicle. For example, to determine the energy cost per mile of an electric vehicle, select the location on the left axis (Electricity Cost per kWh) at $0.09 in the graph below. Draw a horizontal line to the right until you bisect the EV 3 mile/kWh line. Now draw a vertical line down until you bisect the bottom axis (Energy Cost per Mile). This tells you that the fuel for an electric vehicle with an energy efficiency of 3 mile/kWh costs about $0.03/mile when electricity costs $0.09/kWh.



The national average cost for electricity in the United States is about $0.075/kWh, while the average residential rate is about $0.089/kWh. Some electric utilities have had electric vehicle charging rates that vary by time of use, day, and season. These rates can range from $0.03 to $0.50/kWh. Older electric vehicles have energy efficiencies of about 2 mile/kWh. Some electric vehicles, such as the EV1 from General Motors, had energy efficiencies of over 6 mile/kWh.

To determine the energy cost per mile of a gasoline vehicle, pick the location on the right axis (Gasoline Cost per gallon) at $2.50. Draw a horizontal line to the left until you bisect the Gas 18 mile/gal line. Now draw a vertical line down until you bisect the bottom axis (Energy Cost per Mile). This tells you that the fuel for a gasoline vehicle with an energy efficiency of 18 mile/gal costs about $0.139/mile when gasoline costs $2.50/gallon.

The mileage for commercial fleet vehicles, such as light-duty pickups, ranges from below 17 to about 22 mile/gal. The energy cost per mile is also included for a hybrid electric vehicle with an energy efficiency of 40 mile/gal, as these types of vehicles are increasingly being used.

http://www1.eere.energy.gov/vehiclesandfuels/avta/light_duty/fsev/fsev_gas_elec2.html

[chaska]

1. John Michael Greer on the electric car

For those Americans who actually do find themselves in need of a car, how about the new electric vehicles? Will they really decrease your carbon footprint and your fossil fuel use, as so much current verbiage claims?

The answer is unfortunately no. First of all, as already mentioned, the vast majority of electricity in America and elsewhere comes from coal and natural gas, and so choosing an electric car simply means that the carbon dioxide you generate comes out of a smokestack at a power plant rather than the tailpipe of your car. The internal combustion engine is an inefficient way of turning fuel into motion – around 3/4 of the energy in a gallon of gas becomes low-grade heat dumped into the atmosphere via the radiator, leaving only a quarter to keep you rolling down the road – but the processes of turning fossil fuel into heat and heat into electricity, storing the electricity in a battery and extracting it again, and then turning the electricity into motion is less efficient still, so you’re getting less of the original fossil fuel energy turned into distance traveled than you would in an ordinary car. This means that you’d be burning more fossil fuel to power your car even if the power plant was burning petroleum, and since it isn’t – and coal and natural gas contain much less energy per unit of volume than petroleum distillates do – you’re burning quite a bit more fossil fuel, and dumping quite a bit more carbon in the atmosphere, than a petroleum-powered car would do.

This isn’t something you’ll see discussed very often in e-car websites and sales flyers. It’s even less likely that you’ll find any mention there of the second factor that needs to be discussed, which is the energy cost of manufacture. An automobile, petroleum-powered or electric, is a very complicated piece of hardware, and every part of it comes into being through a process of manufacture that starts at an assortment of mines, oil wells, and the like, and proceeds through refineries, factories, warehouses, and assembly plants, linked together by long supply chains via train, truck or ship. All this costs energy. Working out the exact energy cost per car would be a huge project, since it would involve tracking the energy used to produce and distribute every last screw, drop of solvent, etc., but it’s probably safe to say that a large fraction of the total energy used in a car’s lifespan is used up before the car reaches the dealer. Electric cars are as subject to this rule as petroleum-powered ones.

The energy cost of manufacture has generally been downplayed in discussions of energy issues, where it hasn’t been banished altogether to whichever corner of the outer darkness it is that provides a home for unwanted facts. (I’ve long suspected that this is not too far from “Away,” the place where pollution goes in the parallel universe that cornucopians apparently inhabit.) Promoters of the more grandiose end of alternative-energy projects – the solar power satellites and Nevada-sized algae farms that crop up so regularly when people are trying to ignore the reality of ecological limits – are particularly prone to brush aside the energy cost of manufacture with high-grade handwaving, but the same sort of evasion pervades nearly all thinking about energy these days. I’ve mentioned before that three centuries of cheap abundant fossil fuel energy have imposed lasting distortions on the modern mind; this is an example.

Still, factor in the energy cost of manufacture, and there actually is an answer to the question we’ve just been considering. If you really feel you have to have a car, what kind involves the smallest carbon footprint and the least overall energy use? A used one.

I suppose it’s just possible that one or two of the readers of this blog will remember a strange and politically edgy comic strip from the Sixties named Odd Bodkins. The rest of you will just have to forgive a bit of relevant reminiscence here. Somewhere between an encounter with the dreaded Were-Chicken of Petaluma and a journey to Mars with Five Dollar Bill, I think it was, the Norton-riding main character, Hugh, and his sidekick Fred the Bird had a run-in with General Injuns – the resemblance to the name of a certain large American automotive corporation was not accidental. I forget what it was that inspired Fred the Bird to shout “Buy a used car!” but the General’s response – “BLASPHEMY!!!” – was memorably rendered, and will probably be duplicated in a good many of the responses to this week’s blog. Most people in the industrial world nowadays are so used to thinking of the best option as new and shiny by definition, that the homely option of picking up a cheap used car as a way of saving energy is likely to offend them at a cellular level.

Still, the energy cost of manufacture needs to be taken into account. If you buy a used car – let’s say, for the sake of argument, a ten-year-old compact with decent gas mileage – instead of a new electric car, you’ve just salvaged the energy cost of manufacture that went into the used car, most of which would otherwise have been wasted, and saved all the energy that would have been spent to produce, ship, and assemble every part of the new car. Since it’s a ten-year-old compact rather than a brand new e-car, furthermore, you’re not going to be tempted to drive it all over the place to show everyone how ecologically conscious you are; in fact, you may just be embarrassed enough to leave it in your driveway when you don’t actually need it, thus saving another good-sized chunk of energy. Finally, of course, the price difference between a brand new Nissan Leaf and a ten-year-old compact will buy you a solar water heating system, installation included, with enough left over to completely weatherize an average American home. It’s a win-win situation for everything but your ego.

[madokie]

3. There so many holes in that it would be hard to start

but here goes. Natural gas is cleaner burning than either diesel or gasoline so take that out of your spiel, most EV's are charged at night when the power companies have to keep the generators running even though they don't have any market for it at those hours so take that out of your reply so whats left is right wing coal, oil and nuclear energy industry bullshit. Its called spinning reserve or something like that.
You can't simply ramp up a coal or nuclear plant like you can hydro, which by the way is about 20% of our electricity produced. Natural gas and hydro both are easy to ramp up production relative to coal or nuclear. I think you need to maybe give some more serious thought before you post bull like this was/is

Electric motors are in the 95% to 97% efficiency so take that non fact out of your reply and after that not much else left but the fart part of the taking a shit on the OP's post.

with all due respect of course

ETA: I'm not able to find the exact percent of hydro so I may be wrong there but best I remember its somewhere around 20% correct me if I'm wrong.

[GliderGuider]

4. I was thinking that it would have been nice if Greer had included some numbers

About halfway through the excerpt I realized why he hadn't.

I liked JMG a lot when I first found his "Catabolic Collapse" theory, but now he seems like just another arrogant hand-waver with better-than-average grammar. And believe me when I say I know what those look like

[madokie]

5. That same article was in the paper that the local rural electric co-op puts out

a few months back. I was like floored that they'd even include it in their paper. Somethings just can't be explained I guess.

One of my older brothers was using the article as an argument against ev's. I just shook my head and walked away, went on to something else. I knew I didn't want to hear anymore of that crap. In the mean time it told me a lot that I had suspected but didn't know for sure about my brother. He's my brother I love him but I now walk a wide circle around anything about the real world with him any more. I suspect he watches fox noise too.

[PamW]

9. WRONG!!!!!

Natural gas is cleaner burning than either diesel or gasoline so take that out of your spiel, most EV's are charged at night when the power companies have to keep the generators running even though they don't have any market for it
===============================

First, gas isn't really cleaner that petroleum in terms of carbon emission. They all give you CO2.

It's a bunch of CRAP that power companies have to keep gas generators running at night.

Power companies use gas turbines, and gas turbines are really just jet engines with more turbine blades.

Do airlines have to keep the jet engines on their airliners running at night for some perverse reason?
NO!!

Additionally, a power company has to match the generation to the demand. If they generate some energy and it isn't used - where does it go? The grid doesn't store energy, and the Law of Conservation of Energy says that energy just doesn't disappear.

No - as electric demand changes during the day, and night, the power company has to MATCH that demand with their generation. It means that they throttle the plants to meet demand. If demand goes so low that they don't need a plant; they can idle it.

The ones that they idle are the gas turbines; because again they are just JET ENGINES!!!

I don't know who told you that jet engines ( gas turbines ) have to be run all the time; but they LIED to you.

I've read so much NONSENSE on this forum about generating technologies. I've had people tell me that the steam turbines have to turn at night so they don't warp. Power companies routinely shutdown power plants for days or weeks to do maintenance on the steam turbines. In a nuclear plant, that is done during the refueling outage to kill two birds with one stone. So how come the turbines don't warp during extended maintenance shutdowns, but they will warp over night?

Why would engineers design something that destroys itself if it can't run? Why would an engineer design a jet engine that had to be run all night when the plane isn't flying? Why would engineers do that???

No - engines are plenty strong to take the stresses that they endure during operation. Gravity is the WEAKEST of the fundamental physics forces. The only time gravity has a big effect is when there is a huge amount of mass like with a planet or star.

But engines support themselves just fine; like all the products in your house that you use everyday and don't have to keep running.

PamW

[PamW]

11. CORRECT!!

Very good. I've always stated that an electric car can be no more efficient, or no more climate friendly than the power plant used to charge the batteries.

Since most of the electric power in the USA is from carbon-based fossil fuels; by switching to an electric, one is just moving the source of the pollution from the tailpipe to the smokestack of a power plant.

There's also about a 7% average loss in the power lines. So the power plant has to generate 7% more energy to compensate; with 7% more pollution. Additionally, batteries and chargers are not 100% efficient either. Nickel-Metal-Hydride batteries give you back about 2/3 the energy you put in.

So many quote the high efficiency of the electric motor as if it were the only loss mechanism.

In point of fact, the motor is NOT the engine. If anything a motor is analogous to a transmission.

Warning Science content: In Science, an engine takes a fuel input and outputs work ( useful energy ).
A motor takes in work and output work in another form. Electricity is not a fuel, it is a form of work ( energy without entropy ). An electric motor takes in work ( electricity ) and outputs work in the form of rotary motion. A transmission takes in work as rotary motion and outputs work as rotary motion of a different speed. So a motor is analogous to a transmission and not an engine. The power plant is analogous to the engine.

From a carbon footprint point of view, the only place an electric car makes sense from a carbon footprint point of view is in northern Illinois. The Commonwealth Edison service area is so heavily based on low-carbon nuclear power that it is the only place that makes EVs carbon friendly. Anyone in the Commonwealth Edison area; I support your choice of EV. I can't make the same recommendation for anywhere else.

PamW

[kristopher]

37. See post #25

[PamW]

41. Nothing there

Kris,

I see absolutely NOTHING in your post #25 that contradicts what I said.

There's nothing that contradicts that motors are not engines, or that you have 7% additional loss due to power lines.

There's nothing that contradicts that an EV is no cleaner than the power plant used to charge the batteries.

Throwing random data around and then claiming that you made a cogent argument is not persuasive.

PamW

[kristopher]

43. It categorically refutes your conclusion

You wrote:

From a carbon footprint point of view, the only place an electric car makes sense from a carbon footprint point of view is in northern Illinois. The Commonwealth Edison service area is so heavily based on low-carbon nuclear power that it is the only place that makes EVs carbon friendly. Anyone in the Commonwealth Edison area; I support your choice of EV. I can't make the same recommendation for anywhere else.

[kristopher]

25. Comparison of CO2 emissions by various technologies under differing policies

Fig. 5.8


Evolution of emissions per mile by type of vehicle technology through 2100 in the a) No Policy and b) 450ppm Policy cases using the emissions intensity of the average grid mix in each year.



Coal-fired electricity only is shown for the c) No Policy and d) 450ppm Policy cases. Biofuels are not available.
"Prospects for Plug-in Hybrid Electric Vehicles in the United States: A General Equilibrium Analysis" by Valerie Jean Karplus MIT 2008
Pg 60, 61

[liberal N proud]

2. Another factor to consider when looking hybrid/elecrtic vehicles is climate.

Temperature effects efficiency, because you need to heat and cool the passenger cabin, hybrid engine is required to run bringing down the advertised ranges.

[madokie]

6. I think that most if not all heat the seats and steering wheel rather than the air in the vehicle

according to EV world there is very little loss in distance traveled because of the heating needs, air conditioner also. Heated and air conditioned seats are way more efficient than heating or cooling the whole car. For the most part that is a non issue. IMHO

[Fumesucker]

7. You aren't going to get away with cooling the seats only in the south..

Sorry, the car is 120 or hotter when you get in after even a brief time in the summer sun.

When it's over 100 and humid, you will remain a sticky mess unless the air around you is cooled to a reasonable temperature and the humidity reduced.

[txlibdem]

8. Most of the time you'd pre-heat or pre-cool the EV before unplugging it

You can do that via the internet, or with your smart phone. So you might not be stepping into a 120 degree vehicle after all.

[PamW]

12. Taxing the batteries.

Whether you trigger by internet or not; the Laws of Physics dictate how much work from the battery one needs to expend to move the heat from inside the car to outside.

That's going to deplete the battery. There's no getting around the Physics that moving heat is an energy intensive process because of the 2nd Law of Thermodynamics.

It doesn't matter how you order it done; the Internet can't magically make heat move from lower temperature to higher temperature without significant work provided by an energy source.

Nicolas Carnot strikes again!

PamW

[txlibdem]

13. How is it taxing the batteries when the car is still plugged in?

Getting it's Carnot-Juice from the electrical grid.

[Fumesucker]

15. You said the EV's would only have cooling for the seats and wheel..

That's what I was responding to.

[dmallind]

17. Draw well under a kilowatt. Heat is the main killer. Even AC isn't too bad. nt

[Fumesucker]

18. The average blow dryer is about a kilowatt..

Try warming your car with a blow dryer in below freezing weather.

The AC load on a car in hot weather is close to that of a small house, the heat input through the windows is extreme and there is little to no insulation. Think how fast a closed car gets baking hot if you leave it in the sun.

[dmallind]

26. Well jeez I can believe you or my car's specs and consumption data

What exactly do you think I meant by the way?

[Fumesucker]

28. Have you actually had it in really hot and humid weather yet?

Didn't realize you have the car, the conversation is too slow to keep track of who is saying what and I end up replying to just the words in the post.. I'll be interested to hear of the real world performance..

[dmallind]

29. In Feb-Mar? No - but try this

Apologies for orientation and quality (I suck with phone cameras and have no editing software) but as you can see full on AC to 60degrees with full fan draws between 1.5 and 2. The car has an 80kW motor although under appropriate acceleration rarely draws more than 40. It's unlikely to ever be used this way.

[Fumesucker]

30. It looks like 11 miles is cut from your range if I'm reading the display correctly..

Is that display calibrated in kilowatts?

Here's an online photo editor that's actually useful BTW, acts a lot like a cut down version of Photoshop, fast too for an online editor.

http://pixlr.com/editor/

[dmallind]

31. The guessometer is called that for a reason. I get 4.6m/kW.

It should be legible but the climate dial goes 1.5-3-4.5-6 kW

[Fumesucker]

33. Ah, some numbers to work with..

If it can draw 6kW and you're doing about 0.2 kW/mile then every hour of operation at that level takes away about 6/0.2 or 30 miles of range. Of course that's only at extreme temps, the closer to room temperature it is the less the load on the climate control.

6 kW is just about 8 hp btw, I think that was the figure discussed for an auto AC earlier in the thread..

[PamW]

35. EXACTLY!!!

Scientifically; you are right on with your analysis.

Yes - the AC on a car uses about 8 HP.

The compressor of the heat pump that is the AC system doesn't know and doesn't care about what is turning it.

The Laws of Physics; namely the 2nd Law of Thermodynamics REQUIRES a certain amount of work to be input to move a certain amount of heat.
At terrestrial temperatures, it's a fairly substantial fraction like 50%. That is to move 2 units of heat; you have to input 1 unit of work.

It doesn't matter how that work is derived; again if it takes 8 HP from an ICE engine to drive the AC compressor, then it will take 8 HP from an electric motor in an EV to drive the same compressor to move the same amount of heat.

I don't know where the EV proponents think they get "excused" from the Laws of Physics just because they have an EV.

PamW

[kristopher]

36. Perhaps you could document the draw of a modern auto AC compressor.

A specific product with technical specifications would be great, thanks.

[Fumesucker]

38. I found this article about electrically driven compressors for cars..

http://www.epa.gov/cppd/Presentations/Matsunaga%20electric%20inverter.pdf

[dmallind]

39. So let's say this wild scenario is actually real.

Even though I have a pic of max AC pulling <2, let's say 6 is possible because the dial says so (all cars of course have dials that only show usable range - which means my old 91 Taurus could do 140mph). Let's further say I live in the equatorial jungle and ALWAYS run it like that and thus get 30 miles less from every recharge. So instead of about 90 (there is only 20-21kWh usable from the 24) I get 60 miles. 60 miles from 22kWh (some loss there too) of .14c (more than national average for me!) so 60 m on 3.08 = 5.1c/mile

That's equal to 75mpg. And it's impossibly bad for the Leaf.

[txlibdem]

19. Oh, a misunderstanding. That was not me who posted that.

I think that poster meant that after having cooled or heated the cabin while still plugged in, then heated/cooled seats and steering wheel would be enough to get you to your destination. That would work here in Dallas for only a couple of months in the spring and perhaps 1 or 2 months in the fall/early winter. In parts of the country where the climate is milder then more months would be A/C- and heater-free.

I don't believe that would work here in Dallas in the summer. And I know everyone's going to cry for me when I say that it gets kinda cold here in Dallas in winter as well. Thus, I'd be using the air conditioner in summer and the heater in winter. But I am not worried about "running out of juice" because I know how far the drive is and I know how much range the battery has.

Plus, many employers are beginning to install electric car charging stations at work to provide enticement for those workers who would want to drive electric. It may become a moot point unless you have an absolutely ridiculous commute of greater than 60 or 70 miles.

[Fumesucker]

20. Oops..

Thanks for the info.. Sounds great, I'm jealous..

[txlibdem]

21. Don't be. When I became disabled I had to cancel my order for the Nissan Leaf

That was a tough day for me, I gotta say. So I'm in the passenger seat only (looks like for the rest of my life from what they say now).

[Fumesucker]

24. Sorry to hear of your troubles..

[txlibdem]

34. No worries

[PamW]

42. My scenario

When the car is home connected to the grid; it's probably in the garage and not getting the full sun load.

What I had in mind is the car has been sitting in the parking lot of the mall while the owner is shopping, and comes out to a hot car.

If the owner wants to cool down the car by calling it on their cell phone; then the work required to cool the car uses energy provide by the battery.

PamW

[txlibdem]

44. Granted, that would drain energy from the battery

However, according to independent testing, the Nissan Leaf loses 30 miles range if you cranked the A/C the whole way and 35-40 miles of range if you had the heater blasting away (along with the Winterizer option for the battery pack).

Since my wife's commute is either 41 or 37 miles (round trip) depending on which road she takes it's a moot point. I'll tell her to keep her toes warm and cozy the whole way.

No biggie. And if her employer installed Level 2 or 3 chargers then we could move another 40 miles away from work and still be happy as a clam driving an electric vehicle.

Pam, I know you don't like electric cars. And that's okay: don't drive one, keep sending your dollars outside of our economy, possibly to fund terrorism. I won't be doing any of that since the electric power our next vehicle will drive on will be generated by an American company that employs American workers (unionized I believe). And the electric utilities PAY TAXES, unlike the slimeball oil companies who've relocated their HQ to a post office box in the Caymans to avoid paying taxes like a patriotic American should do, and gladly.

[madokie]

22. I was just relating what I've read in their promotionals

sorry bro' but I don't and haven't the wherewithall to make a search for a link this morning. I took it for granted it was common knowledge.
Also I read that they use the cooling system for the battery for some of that duty, on the winter needing heat part.
Air conditioning isn't that energy intensive otherwise we wouldn't have heat pumps because they are pretty much an airconditioner that has the capabilities of reversing the fluid/gas flow.

Ford focus ev will be our next vehicle purchase

[PamW]

10. WRONG!!!!!

Heated and air conditioned seats are way more efficient than heating or cooling the whole car. For the most part that is a non issue.
=================================

Sorry - but heating and cooling just the seats isn't going to keep you comfortable in cold midwest and northern winters nor broiling summers in the south.

Also air conditioning loads are not trivial. Again, the 2nd Law of Thermodynamics, a fundamental Law of Nature / Physics that we can not escape or get around places restrictions on how much heat you can transfer for a given amount of input work.

In a typical car; the air conditioning adds about 7 or 8 Horsepower draw on the accessory drive. That is it takes that much to run the air conditioning and provide the energy to pump the heat out.

Now consider that tooling down the road at highway speed; your engine is putting out essentially about 30 to 35 HP; that 7 HP or 8 HP is a non-trivial load.

It's about a 25% effect. If that's what the EV industry calls "very little"; that says a lot about them.

PamW

[greenman3610]

14. watch this vid for a more realistic and optimistic take

[txlibdem]

45. Electric vehicles are the only ones that will get cleaner as they get older

Your old gas guzzler is going to start leaking at the seals, or more friction here or there so it gets fewer miles per gallon. It will only get dirtier as it gets older.

Electric cars get cleaner as the grid gets cleaner. Put a small solar array on your roof and you'll be driving with true zero emissions.

That is the most amazing thing about electric cars.

[dmallind]

16. And the cheapest line is a high estimate

I'm only on my 2nd week of EV use and averaging 4.6m/kWh. More experienced drivers can easily get into high 5's and even 6's from time to time.

I pay about .14/kWh all inclusive. That's right at 3c/mile compared to the 12c for even a very economical 30mpg mixed car (my 4.6 includes city and hwy - so should the ICE). Now after rebates I probably paid 8K more for an EV compared to a comparably equipped car. So on that alone after 90k miles I'll be ahead. Now add in all the oil changes and additional maintenance on the vastly greater number of moving parts in a superheated environment.

And those <90000 miles (probably much less) will all be near silent, sending no money to ME tyrants, and no gas station stops. Oh and the battery will still be under warranty.

Now it's true there are trade offs. No sense buying an EV if you are a 1 car household with frequent long trips to make. But for the vast majority of us who average well under the range of EVs (used cars don't average 30k a year for a reason) for daily needs and have access to multiple cars, it's eventually going to pay for the upfront costs. The environmental benefits are a side issue to me. Of course to me so is the CBA beyond being feasible. I went that way because I like the technology and hate engine noise.

[tinrobot]

23. You're a good driver.

I just finished my first week in my new EV and I'm around 3.6m/kWh.

The acceleration of that electric motor is a great feeling, but it kills my efficiency. I have to learn to resist that temptation.

[dmallind]

27. Do you have hills?

Pretty flat here which helps a lot too. And yes taking advantage of instant torque off the line is both fun and uneconomical . ECO or D by the way?

[tinrobot]

32. It's a mix...

Some hills, some flats, some freeway, come city. I drive in Eco mode as much as possible, which takes a little bit of zoom off the pedal, but not much. I have a BMW Active E, which wants to go fast, so I have to restrain myself. Slowly getting the hang of it, though. My numbers are creeping up slowly.

[dmallind]

40. Not real familiar with the BMW in great detail I'm afraid

But I'm sure it will improve with practice. I was practising "EV driving" from tips in the forums before I got one.

BTW surprised you got the Active E so soon - you must be one of the first. Enjoy!