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With the advent of the Tesla Roadster, a new generation of 100% battery powered car is upon us. It’s about time. But hybrids with extra battery packs, known as “strong hybrids,” and their counterparts, hybrids that you can plug in to recharge, appropriately known as “plug-in hybrids,” are moving out of the hands of tinkerers and into the mainstream.
An interesting study from CalCars.org, entitled “100+ MPG Hybrids” makes the case that cars powered by electricity from the power grid can get over 100 miles to the gallon. This is somewhat misleading – because cars powered from the grid, to the extent they’re using grid electricity stored on-board, are not getting miles per gallon, they’re getting miles per kilowatt-hour.
Assume a car is a strong hybrid, with range on a battery charge sufficient to fulfill a normal daily commute cycle, and assume that the car is a plug-in hybrid, getting recharged at night from the power grid so no gasoline energy whatsoever is used in its daily functions. This is not a huge assumption – these cars are here today, and soon they will make it out of the tinkerer’s garages and onto the dealer’s showroom floors. How much per mile does it cost to drive these cars?
The math isn’t all that challenging if you are really interested in knowing the answer. First of all, assume a gas powered car gets 30 MPG, and gas costs $3.00. This means a gas car costs $.10 per mile to drive.
Next assume a gasoline powered car has an engine that converts the energy in gasoline into mechanical energy at an efficiency of 25%. This is typical; the rest of the energy is lost in extraneous motion, friction and heat. This means that if a gasoline engine were 100% efficient, that same car could go 120 miles on a gallon instead of only 30 miles per gallon.
Here’s where it gets interesting. A battery will recharge and discharge kilowatt-hours from the power grid at an efficiency of 90%. An electric motor will convert electricity into mechanical energy at an efficiency that is also about 90% (the larger the engine the better the efficiency). This means a battery powered electric car will convert kilowatt-hours from the power grid into mechanical energy at an efficiency of over 80% (90% times 90%).
For this reason, a battery powered car can take that same one gallon of gasoline, using the equivalent amount in kilowatt-hours, and go 96 miles, more than three times what a gasoline powered car can do.
The rest is simple. There are 32.91 kilowatt-hours of energy in a gallon of gas, and the market cost consumers pay for kilowatt-hours is about $.10 (this varies widely, but for recharging at night during off-peak rates $.10 is probably on the high side), which means for $3.29 you can drive an electric car 96 miles. That equates to 2.9 miles per kilowatt-hour, or 3.4 cents per mile. Compared to gasoline powered cars, all-electric cars use far less energy to drive the same distance, and consequently cost far less to fuel.
This is why we will see strong hybrids, plug-in hybrids, and 100% battery powered cars on the roads within a few short years. For references and more in-depth explanations of these formulas, read “The Battery Powered Car.”
Comment by kerrry Beauchrt
September 2, 2006 at 7:40 am - #
The major costs for an electric car is not the electricity it uses.
Those who have ever bought a small toy car know that it’s the batteries that cost a fortune. That Tesla you mention uses 6,871 lithion ion cells batteris. Total cost (wholesale) is around $20,000. Life expectency is 4 to 5 years, making battery yearly costs more than $4,000 plus electricity costs of somewhere around $300. A 25 MPG gasoline car driven 12,000 miles has gasoline costs of less than $1,500 for $3 gallon gasoline. Electric cars are EXPENSIVE to own. It has nothing to do with the costs of a kilowatt hour.
And an electric car loses at least 20% of its capacity by the 4th year. Because of its short range, time required for recharging and lack of recharging stations, no electric car can satisfy a person’s driving requirements. It can only function as a second car. A VERY expensive grocery getter.
Comment by Ed Ring
September 2, 2006 at 8:48 am - #
You are absolutely right in the points you make regarding the cost of lithium ion batteries. They have other problems, such as with heat management, and Tesla is banking on a lot of improvements in battery safety and cost in order for a car car like that to become viable for the rest of us.
It’s interesting, the point you are making about the cost of the car itself (as opposed to the cost of operating it) is the same point we make with respect to fuel cell powered cars (of course they cost a lot to operate as well, but that’s another story) in our post http://www.ecoworld.com/blog/2006/05/23/the-hydrogen-hoax/
On the other hand, nickel metal hydride batteries are now down to $3,000 per pack in hybrid cars, maybe double that to make a pack sufficient for a 100% battery powered car (and the EV-1 used modified lead acid batteries, actually). I think a serial hybrid car, where a constant RPM diesel powers an onboard generator to recharge the batteries that power an electric motor – but isn’t itself (the diesel) connected to the drive train – is a less complex way to build a hybrid car, and potentially more viable.
I believe we are getting close to seeing electric cars that are affordable for commute cycles – where they have a daily range requirement of 100 miles or less. At least the Tesla puts to rest the notion that electric cars have no power.
Comment by Tom King
September 3, 2006 at 8:56 am - #
Remember when Bill Gates said that computers would never need more than 640K of RAM? The statement made complete sense at the time but the trends were all against him, just like they against gasoline cars today. The gorgeous electric Xebra PK pickup truck costs only 10,000 even when produced in tiny numbers. Yes it’d be nice to have a little more speed and range, but the writing is on the wall. Batteries are improving in leaps and bounds while gasoline prices won’t be stopping at 3,4,5, or even 6 bucks a gallon. To forecast the future, ignore the small obstacles and pay attention to the overall trend.
Comment by Brian Schend
September 3, 2006 at 7:05 pm - #
As far as price – Maybe it is $20,000 for batteries, but if you look at the Mitsubishi Miev electric prototype, you will notice that there is no cooling system, no drive train, no differential and no transmission. All of that stuff costs money to produce initially, and all break down a lot more than a modern battery. Today’s lithium-ion batteries don’t go bad after 4 years, and the NiMH batteries in the 1999 Prius have yet to fail or lose charge.
Comment by Kyle Hester
September 4, 2006 at 12:24 am - #
Regarding the Tesla and battery cost. When you buy a Ferrari, the cost of the vehicle is what it is because of what the vehicle can do. To over simplify the Tesla by speaking in terms of battery cost is missing the point. Battery cost will come down with supply and demand.
Comment by David Beard
September 4, 2006 at 8:57 am - #
Actually the Generation II EV1 had NiMh batteries, But in a larger format than is being used in current hybrids. Allot of the problems associated with Lithium batteries are chemistry specific. Lithium cobalt has a tendency to catch fire, slip into a condition called thermal runaway, or explode. This is due to the fact that the chemical reaction of cobalt releases oxygen during a fire..which fuels the fire. Lithium phosphate chemistries do not exhibit this tendency…In short they are inherently much safer. Unfortunately this safety comes at the sacrifice of some energy density. But it is a trade off we can live with. Nanotechnology is bringing improvements in battery technology and Lithiums in the pipeline are now capable of much higher charge/discharge rates…ultimately this will lead to smaller packs and some reduced costs.
Other improvements can be found in changing the way cars are built too….composite materials can be cost effective and competitive with steel, but the manufacturing requirements are different. extensive use of plastics though has some hiddn advantages such as reduced parts count. A part that was traditional made up of several pieces of steel can be molded in a single piece, cutting costs and assembly times. Colors can molded directly into the part, avoiding the need to paint the car.
Comment by John Spradley
September 4, 2006 at 9:29 am - #
Not all electric cars are the same. I have less than $7000 in my
25 year old conversion, including $1300 for new Lead Acid batteries. My gas bill went from $298 in May to ZERO in July and August.
My solar roof-top system pays for all the electricity.
Maintenance? Tires, Brakes, suspension. I calculate my 1981
Ford Electrica is good for another 25 years. Simple. Reliable, easy
to maintain. My 2nd car, a Chevy 3500 van gets about 11 miles per gallon.
True, I gave up a lot, but I gained much more!
Comment by Skarrin
September 5, 2006 at 12:50 am - #
“And an electric car loses at least 20% of its capacity by the 4th year.”
A minor problem with this apodictic statement is that the NiCd batteries in my ‘95 Renault Express are so ignorant about this “fact”, that they still have more than rated capacity (147 instead of 136 Ah) after 11 years.
And those people who already drove >60k miles in a Think city, >50k miles with a Twike, or >150k miles with RAV4 EVs without replacing the batteries, must all be aliens from a parallel universe.
The biggest problem with EVs are uninformed and clueless people completely ignoring facts, and not willing to learn.
Comment by Patrick Wright
September 20, 2006 at 12:14 pm - #
I never understand why people think there is a lack of charging stations for electric cars. Almost every garage in the country has a 110v outlet. I’ve kept a driving record for many years and have found that I drive more than 200 miles in a day approximately 5 times a year. If I had an electric car my “fuel tank” would be full every morning – I wouldn’t need charging stations scattered all over town.
Comment by Dave Robert
September 22, 2006 at 5:10 pm - #
The laws of thermodynamics that limit internal combustion engine efficiency are also acting on power plants as well. You’ve entirely neglected the waste heat that’s part of the combustion cycle at the power plant. A high quality combined cycle gas turbine might yield a maximum of 60% efficiency if you’re doing electricity only. Applying that factor to your equation gives a result of about 50% efficiency, i.e. 80% x 60%=48%. That would get you about 60 MPG equivalent. Not bad, but it’s not 96.
Comment by Brian schend
October 2, 2006 at 4:56 pm - #
60% Efficiency at the power plant x 80% at the car is valid. So let’s add drilling, refining, and truck transport to gasoline. While pipeline is comparable to transmission lines in efficiency, they don’t go to every home like power lines do. So, considering refining, drilling and trucking, gasoline would likewise drop to around 15 MPG equivalent under this scenario.
Hey, if you’re gonna count production and distribution against the electric car, you should charge it against the gasoline car as well.
Comment by David Grove
October 31, 2006 at 3:44 pm - #
“Hey, if you’re gonna count production and distribution against the electric car, you should charge it against the gasoline car as well.”
The important thing is to start at the same starting place and measure the cost from there. Start from a gallon of gasoline. Then use it either to power a conventional automobile, or, alternatively, to fuel an electric power plant and eventually power an EV.
Both require the same starting point. The upstream petroleum production costs accrue to both.
To make the EV vs IC powered behicle comparison by basing the electric vehicle cost on energy in electrical form, while basing the ICE vehicle cost on energy in petroleum form isn’t quite legitimate, in my opinion.
One could make the argument that electricity to power an EV need not be based on a petroleum product if one is considering nuclear, hydroelectric, or coal sources for electricity production.
Comment by nikhil.p.jadhav
April 2, 2007 at 6:52 am - #
hi i am a engineering student and would like to give a seminar on nuclear powered car so can you give any information so that i can give this seminar thanking you
Comment by sculptor
June 24, 2007 at 12:54 am - #
Well, since most of the salient points where addressed in the above discussion I’ll only add that it’s nice (and more efficient) to have an IC vehicle during cold weather because the waste heat can be used to keep ones feet warm. This is called co-generation and it is very efficient if used correctly.
My idea of an ideal vehicle would be a plug-able diesel hybrid. It would get about 70 mpg on the highway and 80 mpg in city driving when it’s off the grid.
Comment by Brooklands
June 25, 2008 at 4:05 pm - #
I am no engineer or expert on any of this, but i would think that if we can have transportation modules using electricity made from coal, hydro, solar, wind, or other sources, as well as hydrogen fuel cells, IC petroleum engines, and anything else that develops, our resources across the world will be better utilized and meet more needs for particular vehicles.
Comment by ben howser
November 22, 2008 at 9:55 am - #
You compare the efficiency of turning gasoline into mechanical energy (25%) with the efficiency of turning electricity into mechanical energy (80%). Fine. But in making the cost comparison, you make the inherent assumption that the gasoline was turned into electrical power at 100% efficiency. However, typical electric power plant efficiency is approximately only 37%. This is the ratio of electrical energy per chemical energy in the fossil fuel being burned to create that energy. Therefore the net efficiency of the electric car powered by a fossil fuel burning power station is only 30%, just slightly above the efficiency of burning the fuel directly in the vehicle.
Comment by dj Galate
February 2, 2009 at 6:23 pm - #
Thank you for all the calcualtions.
Unless I missed it, you folks did not factor in federal and state taxes on Gasoline. Gasoline itself is really pretty cheap.
You can be sure our fine friends at the State and Federal level will not allow people using the roads in electric cars to get away without paying fuel taxes very long.
After adding the taxes to the electric car (per 33 kilowatt/ hr equal to taxes on a gallon of gasoline) I suspect the annual fuel/ total mileage costs, between electric and gas, will be much closer.
My two cents
Dj
PS Be careful what you wish for. Watch for that mandatory, prepaid, Kilowatt/hr meter. It will be installed in all electric/hybrid vehicles that draw electric power from any stationary source (grid, generator,other). They will then start taxing you a Kilowatt road tax from that meter (kind of like a prepaid, automatic, toll collector. If you don’t pay (prepay your meter when you charge up), a little red light on top of your car will light up so they can easily identify and ticket you. The fines and penalties will probably be added as if you ran a toll.
Comment by Dimitris T
February 23, 2009 at 5:47 am - #
However your calculations miss one important part: how was the electricity to charge the batteries generated ?
It comes from a power plant, which, is about 30% efficient in converting nuclear/petrol/carbon/whatever power into electricity. I believe therefore that, when we look at the big picture, it is unfair to state that “IC engine = 25% eff, electric = 80% eff.”
As many people have indicated, the real limitation is the battery technology. All other things are already there.
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April 24, 2009 at 5:26 am - #
[...] a mile — a third of what a 30 mile per gallon car costs to drive with gas at $3 (hat tip Ecoworld). So Better Place would be making $15 million a year in revenue. Not bad, [...]
Comment by Bruce Zanetta
August 17, 2009 at 9:01 pm - #
This appears to be a very good “yardstick” way of comparing mpg to mpkw at least while our mpg society makes the mental transition to kw(h) or caloric or juels or carbon positive or….
Some previous criticisms miss the measurement mark here. This starts with cost to consumer. What you pay at the pump and what you pay at the meter. Start your efficiency calcs from there.
If this were well to wheel comparison then yes the plant efficiencies and electrical transmission losses would have to be included (both require mining, transport and refining of fuels so roughly a wash). Ultimately well to wheel and total cost to society will be built into the better yardstick. But we have to work our way up the learning curve first.
Real world batteries (electric to chemical to electric conversion) are less than 80% efficient and the 300 plus extra energy storage lbs need to be factored in; however, since regenerative braking was not factored in, its probably close enough.
For now I like this price tag to the consumer approach. Tomorrow we will work on the TOTAL price tag to society.
Comment by Elwood Anderson
August 23, 2009 at 12:41 pm - #
It seems to me using the ideal conversion efficiency of 90% for electric is very optimistic. Driving habits would affect this. Although electric vehicles recover some of the energy used in accelerating to road speed when they slow down and stop, there is bound to be energy losses for braking that would reduce the efficiency from the ideal. As one writer has pointed out, efficiency of battery systems drops over time of use, as well.
There have been experimental electric vehicles on the road for some time now. The real miles/kw-hr for those vehicles should be available and would give a better estimate of the actual cost of operating electric vehicles relative to internal combustion alternatives.
Comment by Elwood Anderson
August 23, 2009 at 1:26 pm - #
I have managed to find some real cost data for electric vehicles.
http://evhelp.com/Cost.htm
This gentleman’s cost for a real electric vehicle was 6.5 cents/mi with an electricity cost of 11.8 cents/kwh in 2008. With gas at $2.50/gal this would be the equivalent of a 38 mile/gal internal combustion vehicle. Now the question becomes what type of IC vehicle has the the performance equivalent to this all electric vehicle, and the answer seems to be that any hybrid vehicle now being offered for sale has this performance.
A second data point for EV cost (5.9 cents/mile), including a detailed cost analysis, is given at this site: http://www.ccds.charlotte.nc.us/~jarrett/EV/cost.php
A plot that enables comparison of gas and electric vehicles over a range of performance values is given at this site:
http://www1.eere.energy.gov/vehiclesandfuels/avta/light_duty/fsev/fsev_gas_elec2.html
Comment by Larry Towne
August 29, 2009 at 12:06 am - #
What if you were to marry wind generation, solar generation and extend the range to 0 mpg I have plans drawn up for just such a system.
Comment by Bob Wallace
September 10, 2009 at 1:41 pm - #
“However your calculations miss one important part: how was the electricity to charge the batteries generated ?
It comes from a power plant, which, is about 30% efficient in converting nuclear/petrol/carbon/whatever power into electricity. I believe therefore that, when we look at the big picture, it is unfair to state that “IC engine = 25% eff, electric = 80% eff.””
The article is about cost to driver, not where the cost of purchased gas/electricity derives. And the efficiency statements are about ICE vs. EV cars.
But if you wish to address the ‘where does the electricity come from’ issue, less than 50% of our electricity now comes from coal. It dropped to 46% last year. And we increased our production from renewables from 9.4% in 2006 to 13% this year.
Now here’s another interesting tidbit (based on DOE numbers)…
To extract one gallon of gasoline (or equivalent distillate): 9.66 kWh
To refine that gallon: 2.73 kWh additional energy.
Total: 12.39 kWh per gallon.
EVs use about 0.25 kWh per mile. There’s enough electricity used to extract and refine one gallon of gas to power an EV 49.6 miles.
Every EV that takes an ICE off the road automatically creates its on supply of electricity.
Comment by arne
September 16, 2009 at 10:03 pm - #
Very informative article and comments, but here is something I have never heard talked about.
As 100% electric cars powered off the grid come to market and begin to achieve a net % reduction in motor fuel consumption, what new tax will be created in order to replace the loss in fuel tax revenues that “in theory” are supposed to be used to fund road construction and repair? Will state and local governments along with the US Government implement a tax on all electricity?
Comment by peter
September 20, 2009 at 3:50 pm - #
Yet another cost comparison would be the cost of each automobile and the estimated maintenance required on both. I wonder what the life expectancy of a gas motor vs. electric is and the cost of tune-ups vs. new batts. Also the environmental impact of discarding or recycling each at the end of the life cycle.
Comment by Bob
September 30, 2009 at 8:13 am - #
Instead of assuming 30 mpg for the gas vehicle ltake a smart car at 50mpg as our starting point.
Based on the calculations above, the 100% efficiency point is now equivalent to 200 mpg. The electric vehicle jumps to an equivalency of 160 mpg instead of 96. What’s wrong with this picture.
Am I missing something or is the assumption that electric vehicle efficiency is directly related to gas vehicle efficiency valid?
Comment by Neil
October 9, 2009 at 4:04 am - #
I agree that the efficiency should include the fuel burnt at the power station, which makes the comparison much closer. I also think that although the ‘wallet’ cost to the consumer is essential in getting people to change habits – the real cost is in terms of carbon dioxide emissions – this is the crucial factor for me and burning coal to power ‘clean’ EV is plain stupid.