Cost of driving: electricity vs. gasoline

[Wordsmith]

Hello All,

I'm trying to get a sense of the cost of using electricity e.g., plug-in hybrid vs. the cost of operating the same vehicle using gasoline. I've read a comparison using the btu value of gasoline vs watts/btu but I'm not sold on that idea since the vast majority of thermal energy in an automobile goes out the tailpipe. What I was thinking of was choosing a 'standard' car like a Ford Taurus, operated on a highway at a steady state for one hour. Using horsepower as the common denominator between gasoline and electricity As far as gasoline consumption, I would propose dividing the miles traveled in the hour by some reasonable highway MPG. Just for sake of example, I have read that steady-state 50 MPH driving uses 40 HP. Figuring 25 MPG highway, gasoline at $4.00/gal and electricity (746 W/hp * 40 hp. for one hour = 29.84 KWH. At $0.10/KWH, driving the 50 miles cost $2.98 using electricity or 2 gallons of gas = $8.00.

Obviously, the example is greatly simplified, but is it a fair comparison?
Thanks for your thoughts.
Wordsmith

 

[russ_watters]

You are right that most of the energy goes out the tailpipe. The efficiency is somewhere around 30%. The easiest way to deal with that is to divide the fuel economy by the efficiency to find the equivalent economy of a plug-in hybrid.

Ie, a car that gets 40mpg would get an equivalent 40/.3= 133 mpg.

There are certainly other complicating factors, but that should get you in the ballpark.

 

[RonL]

Although I don't agree with all he says, there are a lot of things worth considering in this presentation.

It might be a little help to some.

http://ludens.cl/philo/electric.html

 

[rbj]

Although I don't agree with all he says, there are a lot of things worth considering in this presentation.

It might be a little help to some.

http://ludens.cl/philo/electric.html

this looks interesting. even though i am an electric car advocate (and had been for some time), i am not sure that i disagree with this guy (the author, Manfred Mornhinweg, XQ2FOD, looks like he's an amateur radio operator licensed in Chile) about the facts.

when you take a Thermodynamics course in mechanical engineering, you will learn about the ideal Carnot Cycle, entropy, and the difference between "high-grade energy" (ordered mechanical energy such as the twist of a shaft or electricity) and "low-grade energy" (essentially heat). when converting from Joules of heat to Joules of ordered mechanical energy (via an ideal Carnot Cycle), there is a theoretical maximum efficiency of

1 - \frac{T_{in}}{T_{exhaust}}

where the temperatures are relative to absolute zero, like Kelvin. so, if fuel is burnt to make electricity, the cost of a Joule of electriciy must cost more than a Joule of heat from some combustible fuel (by a factor of at least the reciprocal of that efficiency). so you have to consider the cost of the electric Joules compared to the cost of the gasoline Joules with figure divided by the reciprocal of the efficiency of the engine (from point of sale of the energy source to the axels of the drive wheels). that's how to compare these apples to oranges.

the reason why i might not agree with that ludens.cl guy is that i think that centralized power plants (where the chemical energy of a fuel is converted to heat and then to mechanical power) are far more efficient than the miniature power plants we drag around with us when we drive our conventional cars around (although the technology of both are getting better, but i think that the electric power plants' efficiency is closer to their limit than car engines).

 

[rbj]

another cost you have to consider in the cost of a pure electric car, is the cost of replacing the batteries after their expected life. traction-motor batteries (deep-cycle rechargable batteries either lead-acid or of some modern technology like lithium-nickel) ain't cheap, and after some, i dunno, 10000 kilometers (maybe more, i don't know what the mean lifespan of a battery is, nor precisely the cost), you have to replace and responsibly recycle those batteries. that costs money. serious bucks.

 

[Shackleford]

another cost you have to consider in the cost of a pure electric car, is the cost of replacing the batteries after their expected life. traction-motor batteries (deep-cycle rechargable batteries either lead-acid or of some modern technology like lithium-nickel) ain't cheap, and after some, i dunno, 10000 kilometers (maybe more, i don't know what the mean lifespan of a battery is, nor precisely the cost), you have to replace and responsibly recycle those batteries. that costs money. serious bucks.

Yeah, like a couple grand if I remember correctly. So, the cost effectiveness drops drastically.

 

[LURCH]

I have done considerable figuring on this topic, but took a very different approach from the one in the OP. I took numbers from the one highway EV that I know of (the Tessla), and multiplied the number of kW/h per mile by the price of electricity on my electric bill that month. My conclusion was that driving 25mi would require a certain amount of electrical energy (I think it was about 4kW/hrs; I'll look it up), which I then reffered to as an electric gallon, or EG. From my calculations, driving about on electrical energy would be about $1.00/USgal (that's assuming the electricity gets taxed like petrol, about $.40/EG).

I also figure the CO₂ emmisions would be about 1/2 that of gas (and that assumes no improvement over current rates of CO₂ per kW/hr).

 

[rcgldr]

I also figure the CO₂ emmisions would be about 1/2 that of gas (and that assumes no improvement over current rates of CO₂ per kW/hr).

Unless your source of electricity is from a coal burning plant.

 

[montoyas7940]

Unless your source of electricity is from a coal burning plant.

How would CO2 emissions compare if it were from a coal burning plant?

 

[rcgldr]

How would CO2 emissions compare if it were from a coal burning plant?

I don't know the exact numbers, but...

Coal is the major fuel used to generate electricity worldwide, but burning it adds more carbon dioxide, a greenhouse gas, to the atmosphere per unit of heat than does burning other fossil fuels like oil and natural gas.

http://www.america.gov/st/washfile-english/2007/May/20070530134219lcnirellep0.6537592.html

How toxic are the li-poly batteries used in electric vehicles? Can these be recycled? What's the loss in energy in having to produce electricity, transmit it, charge up batteries, which have to store it, then convert it into linear power to propel a car, as opposed to extracting, tranporting, and storage of gasoline, where all the conversion into linear power occurs within the car?

 

[LURCH]

Unless your source of electricity is from a coal burning plant.

No, that's assuming the electricity comes from nothing but a coal-burning power plant, one with no better carbon control techniques than those currently in use.

 

[LURCH]

Ah, here is that research I did:

As can be seen from this site...
http://www.teslamotors.com/efficiency/well_to_wheel.php
...the Tesla requires about 110Wh to travel 1km. This translates to about 160Wh/m. According to the EPA, the average passeneger vehicle gets about 25mpg, so multiplying 160Wh/m by 25mpg, we get 4000Wh = 1gal. This is to establish what I call the Electric Gallon (or EG), which is the amount of electrical energy required to drive the same distance as 1 gallon of gasoline; 4 kWh.
Looking at my electric bill from last month, I see that I am paying about 10 cents per kilowatt hour, including all taxes and service fees. So...
$.10 per kilowatt hour times 4 kilowatt hours gives me about $.40 per EG. Of course, if electricity is being sold as fuel for vehicles, the taxes usually charged for gasoline will have to be charged for that electricity in order to maintain roads. Also, if gas stations begin selling electricity, the electric utilities will have to charge at a higher rate, due to the very high current the stations would require. And of course, the fuel stations themselves would have to mark up the price in order to make a profit. Depending on the state in which one lives, gasoline taxes can be anywhere between $.30 and $.50 per gallon...
http://www.energy.ca.gov/gasoline/statistics/gas_taxes_by_state_2002.html
... and the national average is about $.40, bringing the price of electrical energy as automotive fuel up to $.80 per EG. So, even if the electric utility and the fuel distributor really gouge the customer at $.10 per Equivalent Gallon apiece, the price still only goes up to $1.00/EG.


It can also be seen from this DOE web site:
http://www.eia.doe.gov/cneaf/electricity/page/co2_report/co2report.html#electric
that burning coal to generate electricity creates about 2 pounds of CO2 per kilowatt hour. Multiplying by 4 kWh, this renders about 8 pounds of CO2 per EG. By comparison, according to this EPA web site:
http://www.epa.gov/otaq/climate/420f05001.htm
burning gasoline generates approximately 20 pounds of CO2 per gallon; roughly double the amount.

 

[Phrak]

Nice research, Lurch.

I'd add that converting power from the mains to recharge the batteries obtains losses in both battery heat and power conversion, perhaps 15%.

 

[Phrak]

How toxic are the li-poly batteries used in electric vehicles? Can these be recycled? What's the loss in energy in having to produce electricity, transmit it, charge up batteries, which have to store it, then convert it into linear power to propel a car, as opposed to extracting, tranporting, and storage of gasoline, where all the conversion into linear power occurs within the car?

Lithium batteries are still an evolving technology. In the form that I've read about, the lithium is in the form of an olivine, lithium iron phosphate; no heavy metals, which is nice to see. At one time I looking up electric power generation and transmission efficiency. I think 39% is close to nominal.

The cost of coal is about $100 per ton
Nominally 20*10^6 BTU per ton (varies from about 16 to 26 MBTU)
1000 BTU = 293 Watt-hours
about 39% efficiency for delivered energy from the mains
----------------------------------------------------------------
Cost in coal, alone, for delivered power: 4.4 cents per kilowatt-hr

I would have guessed 6 to 7 cents out of 10. But the numbers do seem to be in the right ball park.

So how does gasoline compare to coal in cost?

Coal: 88 KBTU per dollar (using the 10c per KWhr figure)
Gasoline: 125 KBTU per gallon, at $4.00 per gallon obtains 31 KBTU per dollar

Each delivers about 20 - 25% efficiency to the axle.

 

[Littlepig]

Unless your source of electricity is from a coal burning plant.

you are comparing a car's motor efficiency with a power plant efficiency...

anyway, when doing some kind of effectiveness evaluation, you must know what the degree of accuracy you want. first you were only considering a first approximation of the equation: electric versus gasoline, then you start putting terms about battery, and then about effectiveness of electrical energy produced in power plants versus mechanical energy produced by the car with gasoline or with electrical energy. So, at this time, you have already some variables.

however the point is: if you want to know how you do the calc, is one thing, if you want to know what are the variables of it, is other thing... physics can give you both and can give you an equation relating every variable and the optimum solution(if it exists), but you have to say at what level of accuracy you want, otherwise, more some days and we are arguing that at your living place, energy chargers are at x miles, so you will waste more energy to go there than to a conventional fuel station...xD

 

[Phrak]

I've done a little more reasearch in the mean time on coal fueled electric power generation. They are not as efficient as I beleved. Some years ago the hot technology was internal combustion coal dust turbines, but this technology doesn't seem to have made it to general use, so the less efficient boiler-driven steam-turbine seems to be the common motive source.

The efficiency of coal burning electric power generatation is about 35%.
The efficiency of delivery over the power grid (US) averages about 93%.
Overall efficiency. 0.35*0.93 = 32.5%

 

[cspeaker]

Has anyone ever considered the use of Geothermal driven power plants to generate the electricity for electric cars?
Yellowstone has enough geothermal energy to drive all the geothermal electric power plants we would ever need. The only cost would be for plant construction and maintenance. (I know it would require congressional approval to use Yellowstone.)
I can envision the government selling the electricity through separate meters with the electric cars being required to charge at night in order to receive the special pricing and not overload the grid. The revenue from the sales could be used to fund (pick your favorite unfunded liability) or reduce income taxes ... whatever. This would also result in zero CO2 emissions. The revenue could also be used to help lower income families purchase their first electric cars and get the older (cheap) gas hogs of the streets.

This could also be the initial step towards the fuel-cell cars with hydrogen being produced through electrolysis from this new found excess of electricity.

 

[LURCH]

Has anyone ever considered the use of Geothermal driven power plants to generate the electricity for electric cars?

Everybody, but that's a different thread, I think.

This could also be the initial step towards the fuel-cell cars with hydrogen being produced through electrolysis from this new found excess of electricity.

If you've alerady got the cars running on electricity that's produced with zero emissions, what do we need fuel cells for?

 

[OmCheeto]

Hello All,...I have read that steady-state 50 MPH driving uses 40 HP. Figuring 25 MPG highway, gasoline at $4.00/gal and electricity (746 W/hp * 40 hp. for one hour = 29.84 KWH. At $0.10/KWH, driving the 50 miles cost $2.98 using electricity or 2 gallons of gas = $8.00.

Obviously, the example is greatly simplified, but is it a fair comparison?
Thanks for your thoughts.
Wordsmith

Adding together your numbers and my numbers, I come out with $1.92 for a 50 mile trip using solar power.

30 kwh required per trip
45 watts/panel
180 $/panel
8 hours of sun a day
360 wh/day/panel
83.3 panels required
$15,000.00 cost of panels
13,036 miles driven a year
391,071 miles driven in a career(30 years)
$0.038 $/mile over your career

$1.92 cost of 50 mile trip

energy equivalent mpg at $4/gal: 104 mpg
energy equivalent mpg at $5/gal: 130 mpg
energy equivalent mpg at $10/gal: 261 mpg

assuming a lot of course

 

[GTrax]

Some time back, in another thread, I did a estimate comparing what it would take to move my car through a journey if it were powered electric, working it back through all the stages to the power station.

Its not nearly as good as the varied research and approaches in this discussion, but I include the pointer here ..
https://www.physicsforums.com/showpost.php?p=1509048&postcount=46"

 

[Phrak]

Some time back, in another thread, I did a estimate comparing what it would take to move my car through a journey if it were powered electric, working it back through all the stages to the power station.

Its not nearly as good as the varied research and approaches in this discussion, but I include the pointer here ..
https://www.physicsforums.com/showpost.php?p=1509048&postcount=46"

'Read your post, GTrax. Nicely done. There are three main concerns. 1) Fuel cost is primary. It drives the market, and for the most part determines future trend. 2) Fuel efficiency. Interesting to calculate, but does it matter except on how it drives fuel cost? 3) Pollution, which includes CO2 emmisions if we are to believe the hocky-puck graph of global temperature change.

 

[GTrax]

Thanks Phrak
Re: the cost of fuel. Here (UK) it is £1.33 (ukp) per litre. That translates into $10.04 per U.S. gallon at today's exchange rate. It takes $160 to fill my car tank. It burns me up some to know that part of this is driven by those naughty blighters who speculated it up to there, and are going to make a pile later as they drive it down again while selling short.

rant.. rant.. :|

If every there was anyone looking hard to save on it, or seek alternatives, it is me. I find it interesting that the use of bio-fuels has increased hugely in the SA in a very short time. This may be a bit better than using ancient fossil fuel, but I think it just drives a food shortage.

 

[Phrak]

Thanks Phrak
Re: the cost of fuel. Here (UK) it is £1.33 (ukp) per litre. That translates into $10.04 per U.S. gallon at today's exchange rate. It takes $160 to fill my car tank. It burns me up some to know that part of this is driven by those naughty blighters who speculated it up to there, and are going to make a pile later as they drive it down again while selling short.

rant.. rant.. :| .

Yikes @ 10 bucks a gallon. Half those are taxes, aren't they? I hope you're right--about the market dropping out, that is.

If every there was anyone looking hard to save on it, or seek alternatives, it is me.

From my calculations, we should be seeing plug-in electrics merging into the market and supplanting the majority of gasoline powered private transportation within 15 years. (I hope I haven't bungled my calculations.) The fuel cost, in my estimation, will be about 30-40% that of gasoline at current prices. If I recall, England has a good deal of coal reserves. Good for fuel cost, bad for pollution.

I find it interesting that the use of bio-fuels has increased hugely in the SA in a very short time. This may be a bit better than using ancient fossil fuel, but I think it just drives a food shortage.

It's a rare person who can put the pieces together required to understand this energy issue: market forces, the most elementary thermodynamics, mechanical and electrical engineering, and some Newtonian mechanics. A little bit of each. You seem to have a good handle on a majority of it. None of the news media here made the connection, when this news was first circulating, that it could be dangerous ground to have food and methanol competing for the same food supply.

I stood at a busy intersection at rush hour, yesterday. This is an historical aberration that cannot last. Cheap and ready transportation is an incredibly luxury we take for granted. But I've wondered off the folder topic of classical physics, haven't I?

 

[RonL]

Yikes @ 10 bucks a gallon. Half those are taxes, aren't they? I hope you're right--about the market dropping out, that is.
From my calculations, we should be seeing plug-in electrics merging into the market and supplanting the majority of gasoline powered private transportation within 15 years. (I hope I haven't bungled my calculations.) The fuel cost, in my estimation, will be about 30-40% that of gasoline at current prices. If I recall, England has a good deal of coal reserves. Good for fuel cost, bad for pollution.
It's a rare person who can put the pieces together required to understand this energy issue: market forces, the most elementary thermodynamics, mechanical and electrical engineering, and some Newtonian mechanics. A little bit of each. You seem to have a good handle on a majority of it. None of the news media here made the connection, when this news was first circulating, that it could be dangerous ground to have food and methanol competing for the same food supply.

I stood at a busy intersection at rush hour, yesterday. This is an historical aberration that cannot last. Cheap and ready transportation is an incredibly luxury we take for granted. But I've wondered off the folder topic of classical physics, haven't I?

It seems like the old saying, something like "Standing too close to a tree, keeps one from seeing the forest" might apply here(for the majority of the population). There might also be a little "war debt repayment" going on.

Ron

 

[GTrax]

Oh boy - have I started to cause controversy? Still - you may have it all without bones or horns.
There now follows a little energy costs polemic. It leads back to to physics - I promise.
The tax fraction on UK fuel has an interesting history, and has at one stage reached an incredible 81.5%.
The present fraction is about 71.5% The mechanism is a fuel duty. Then, the total is re-taxed with VAT, which is a kind of 17.5% sales tax that has been allowed to morph beyond its original application concept.

As with several European countries, the stated aim is to "help the environment" by pricing cars off the road via taxes, which fortuitously also raise revenue for the governments. As to whether we actually need that much government is up for debate, but the treasury came to depend too much on the revenue raised from motorists and transport. A previous government introduced a "fuel escalator" where the price of fuel would automatically be raised by tax at 3% above inflation .. forever!
The arithmetic was inevitable, and the policy was abandoned in 1999. This is a place where physics fellas would say "what were they thinking?", but hardball fact does not drive these decisions. Things had to be media-managed a bit in 2000 when fuel truck drivers blockaded the refineries and depots. In the ensuing chaos, very few blamed the drivers. Universally, they blamed the goverments. For a while, the politicians in office felt real fear. I watched it happen.

Originally, using a diesel vehicle with 22:1 compression ratio, and using a fuel very much cheaper to produce than gasoline petroleum, delivered an efficiency advantage over the 12:1 petrol engines. you could go a lot further for the same spend. Arguing that diesel fuel was very polluting, the government increased the tax on diesel to "equalize" the price at the pumps. Now, it has gone further. Petrol is £1.24 per litre and diesel is £1.33 ( you work it out this time 1 US gallon = 3.785 litres). The result is that now, using diesel delivers a price payoff for a car only if you exceed 40,000 miles annually.

The UK is an oil-producing country. The present fuel crisis is not actually a crisis for the UK government. The tax could have been substantially reduced, without hurting the revenue take. But for all the hand wringing, there is no way they would do that. They want the windfall, and are able to cite "outside factors beyond their control" One irony is that modern diesel engines, aside from being a whole lot more efficient than petrol types, are now possibly also less polluting.

Of course, the scamsters will try to cash in on ignorance. . Like this ..
http://cgi.ebay.com/Water-Fuel-Cell-Car-Conversion-Improve-Mileage-MPG-Kit_W0QQitemZ250257903673QQihZ015QQcategoryZ47103QQcmdZViewItem"

(OK - the link will maybe have a short life) but I had to persuade a friend that water is the very pits of the end of any fuel life. Its like ash! You have got to put in a whole lot of energy to tear that hydrogen back into engine-ready usefulness. We are driven to contemplate biofuel. There cannot be enough used fast food fryer oil to go around, even if we want to get up to a messy conversion process in the garage. What are we going to do? Oh yeah - we can turn whole chunks of the nation into gasahol precursor farms with the help of some genetically engineered plant that will survive the other products we dump on it to kill every other living thing. We can't sell that bio-diversity, so why do we need it? Hmm..

For me, the single greatest gain has come from just not using so much in the first place. My low tech woodburner can keep me through the worst of the winter, and is carbon neutral. A bicycle can replace some journeys. Even if the UK and all its energy use were to disappear instantly, we would offset just the increase in Chinese energy use less than a decade. Maybe only half that! We can all see the danger. We just cannot bring ourselves to give up the life. Clearly, the end result will not be equitable.

Back to physics? It just has to be fusion, if possible P+B11, but D-T via Lithium will do. We have just got to get that to work. Personal mobility need not be an electric car. It can burn Hydrogen, if the technology can make a safe way to deliver it. We can start reclaiming the stuff from the water! Optimism brothers.. it will even work in a big SUV!

 

[Phrak]

Oh boy - have I started to cause controversy? Still - you may have it all without bones or horns.
There now follows a little energy costs polemic. It leads back to to physics - I promise.
The tax fraction on UK fuel has an interesting history, and has at one stage reached an incredible 81.5%.
The present fraction is about 71.5% The mechanism is a fuel duty. Then, the total is re-taxed with VAT, which is a kind of 17.5% sales tax that has been allowed to morph beyond its original application concept.

You're paying 76.5%, overall, in taxes. Recently in the news I heard repeated the 10 US dollar per US gallon figure you quoted, along with truck driver protests in England and India.

You have a way with words, with entertainment in every paragraph, reminding me of Andrew Sullivan (ex pat British columnist in the US, I believe), or Terry Pratchett, British scifi author.

As with several European countries, the stated aim is to "help the environment" by pricing cars off the road via taxes, which fortuitously also raise revenue for the governments. As to whether we actually need that much government is up for debate, but the treasury came to depend too much on the revenue raised from motorists and transport. A previous government introduced a "fuel escalator" where the price of fuel would automatically be raised by tax at 3% above inflation .. forever!
The arithmetic was inevitable, and the policy was abandoned in 1999. This is a place where physics fellas would say "what were they thinking?", but hardball fact does not drive these decisions. Things had to be media-managed a bit in 2000 when fuel truck drivers blockaded the refineries and depots. In the ensuing chaos, very few blamed the drivers. Universally, they blamed the goverments. For a while, the politicians in office felt real fear. I watched it happen.

When our local politicos want money for one thing, they habitually know that they can write a law pretending it will be going to police, firefighters, or school children to gain voter majority. If not one of them cared one wit about the 'environment' it wouldn't stop them for promoting the notion, but I suppose you know all about the political game.

There's an short story about the very first congressional session that meeting for the first time in the United States. A small window had been left cracked open, somewhere on the side of the entrance hall. As the doors were opened the lobbiest were there to greet them.

I think a a more precise comparison of electric plug-ins vs. gasoline (or diesel) costs is nearly in order, complete with decent references. There are a few numbers still missing: 1) battery replacement cost amortised over lifetime of the battery, 2) an EPA figure for an automobile comparable to the Tesla (or has Lurch already found this?) and 3) the drive-train efficiency from the motor, through gearing and transmission, to the axle.

 

[OmCheeto]

I think a a more precise comparison of electric plug-ins vs. gasoline (or diesel) costs is nearly in order, complete with decent references. There are a few numbers still missing: 1) battery replacement cost amortised over lifetime of the battery, 2) an EPA figure for an automobile comparable to the Tesla (or has Lurch already found this?) and 3) the drive-train efficiency from the motor, through gearing and transmission, to the axle.

30 kwh (ref: Wordsmiths baseline energy requirement)
30000 wh
1200 wh / pb battery (ref: written on the top of my battery)
50 pb batteries required (@ 50% discharge, ref: http://www.batteryfaq.org/ )
70 lbs / pb battery (ref: so says my bathroom scale)
3500 weight of pb batteries
$70 cost of a pb battery (ref: according to my receipt)
$3,500 cost of all pb batteries
10 lifespan of the batteries (ref: http://www.batteryfaq.org/ )
$350 annual cost of batteries
$0.03 cost per mile of the batteries
$0.04 cost of the electricity
$0.07 total cost per mile electric

$0.16 cost per mile at $4/gal @ 25mpg



lithium ion (ref: http://en.wikipedia.org/wiki/Lithium_ion_battery )
160 wh/kg
4 wh/$
30000 wh required (ref: Wordsmith again)
187.5 kg (or 400 lbs) required
$7,500 $ required
my conclusion: not much cheaper than gas overall.

Two things pop out of the above numbers above.
We really need a cheap lithium ion battery.
A car getting 50 mpg would have the same per mile cost as the 7000lb pb electric.

But then again, as one of my fellow EV enthusiasts has noted in his signature; "Sunlight will never cost $4/gallon"

 

[Phrak]

30 kwh (ref: Wordsmiths baseline energy requirement)
30000 wh
1200 wh / pb battery (ref: written on the top of my battery)
50 pb batteries required (@ 50% discharge, ref: http://www.batteryfaq.org/ )
70 lbs / pb battery (ref: so says my bathroom scale)
3500 weight of pb batteries
$70 cost of a pb battery (ref: according to my receipt)
$3,500 cost of all pb batteries
10 lifespan of the batteries (ref: http://www.batteryfaq.org/ )

The applicable lifetime figure is in miles, not years.

Here's a quote from a link to that web page:
" A good quality wet deep cycle (or "leisure") battery will cost between $50 and $300 and, if properly maintained and used, will give you at least 200 deep discharge-charge cycles. "

Using your numbers, this is a cost of 3.5K every twenty thousand miles, not counting labor.
Nevermind you have to pay for energy.

Who uses lead in their electric cars?

But then again, as one of my fellow EV enthusiasts has noted in his signature; "Sunlight will never cost $4/gallon"

Bleh,in the real world, some have paid more. As much as sunlight if free, so is gasoline.

 

[OmCheeto]

The applicable lifetime figure is in miles, not years.

Here's a quote from a link to that web page:
" A good quality wet deep cycle (or "leisure") battery will cost between $50 and $300 and, if properly maintained and used, will give you at least 200 deep discharge-charge cycles. "

hmmmm... I missed that quote.

I based my numbers on the following graph:

http://jgdarden.com/batteryfaq/conlife.gif

1000 cycles at 50% discharge.
But you are still correct that my numbers were wrong.
1000 cycles / 200 trips per year = 5 years.
So even the lead hog has the same price per mile as a 25mpg vehicle.

And that's a bit of a weird web site. No matter which page you go to, the url stays the same: (http://www.batteryfaq.org/)
The reference should have been: http://jgdarden.com/batteryfaq/carfaq11.htm

Using your numbers, this is a cost of 3.5K every twenty thousand miles, not counting labor.

I do all my own work.

Nevermind you have to pay for energy.

I inherited the solar panels from my dad. I no longer have to pay for energy. Unless I want more of course.

Who uses lead in their electric cars?

http://www.zapworld.com/"

Primitive, but at least they're trying.

Bleh,in the real world, some have paid more. As much as sunlight if free, so is gasoline.

And black is white, and good is bad, and arbeit macht frei, etc. etc.

Double Bleh!

 

[Phrak]

I inherited the solar panels from my dad. I no longer have to pay for energy. Unless I want more of course.

That's very nice for you, but I doubt your dad will be the charitable institution sufficient to supply the electrical energy needs to the rest of us. We should probably have to pay for our free solar energy.

 

[RonL]

Who uses lead in their electric cars?

Because of low cost, and ease of recycle, I think lead and sulfuric acid are getting a bit of a kick in the pants.

Duration is low, but then so is the average daily commute. I think we are led into a false illusion of how much power and duration we really need.

 

[OmCheeto]

I inherited the solar panels from my dad. I no longer have to pay for energy. Unless I want more of course.

That's very nice for you, but I doubt your dad will be the charitable institution sufficient to supply the electrical energy needs to the rest of us. We should probably have to pay for our free solar energy.

Yes. But you'd have to spend the money on energy anyways. May as well make it clean. And we really don't know how long these panels will last. They may truly be a seventh generation device. Mine have so far made it through two, and are still operating at 100% rated capacity.

On another note, I emailed the gentleman from whom I stole the sunshine quote. He graciously stated that I could distribute any of the following information regarding EV's:

Cost to operate a vehicle is about more than fuel. ICE vehicles need oil, fuel filters, air filters and other things that EVs do not need at all. My EV (Chevy S10EV) does not even have a transmission, it is direct drive. EVs with regenerative braking don't need their brake pads changed as often. All of these need to be considered for a true cost of operation comparison. Also, what about your time (or your employees time) spent going to, from, and at gas stations. EVs charge overnight right in their parking spot and are fully charged each morning ready to go.

Another thing, including the battery replacement cost is misleading unless you are leasing the batteries. Most cars on the road are less than 12 years old. The number I have heard is 90% are newer than 12 years. Take a look next time you are on the road, unless you are at an antique car show, you'll like find this to be true. This means that the 10 year battery pack that will likely come with most EVs will service it for its entire life. There are Toyota RAV4's on the road today that have over 100,000 miles on their original batteries. My EV is a 1998 and it still has its original (NiMH) batteries.

It seemed relevant to the thread topic, so I left it unedited.

I will also be going to the local EV Association's "EV Awareness Day" tomorrow from 9:30 am to 5:00 pm
Pioneer Courthouse Square, Portland, Oregon.
Everyone is invited.

I will see if I can get some real world numbers for the cost of operating these vehicles from people who actually drive them.

 

[GTrax]

We have a very nice costing example with the stress on batterys.

30 kwh (ref: Wordsmiths baseline energy requirement)
30000 wh
1200 wh / pb battery (ref: written on the top of my battery)
... et al ..
We really need a cheap lithium ion battery.
A car getting 50 mpg would have the same per mile cost as the 7000lb pb electric.

It seems to me we have about three things going here.
1) The running cost of a gasoline vehicle, accounting various mandatory bits amortized over the miles the vehicle manages before we try to recover / recycle the dead bits.

2) The running cost of a electric vehicle, accounting a different set of mandatory bits, similarly amortized, this electric vehicle being possibly a notional one that is not in production yet, and might assume a battery technology that is not developed yet.

3) A completely different cost, expressed in terms of the the energy involved in dragging the user around, plus what was expended in the furnaces and mills and microelectronic plants in its creation, plus what it takes to keep it going for its life, plus what it takes to dispose of it, less what it keeps back by recycling long-lived useful stuff, or is recovered to become something else.

As a parting shot - we can figure the amount of fossil-derived carbon this activity would put into the atmosphere, though we know the real cost that will ultimately visit us is hard to quantify right now, but will be paid by our children.

Something like ..
\left[C_{gaso} = \frac{C_{fuel}}{mpg} \,\,+\,\, \frac{C_{tire}*n_{wheels}*m_{life}}{m_{tyre}}\,\,+\,\,\frac{C_{batt}*n_{batt}}{m_{life}}\,\, +\,\,\frac{C_{parts}}{m_{life}}\,\,+\,\,more.of.this\right]

C_{fuel}\,\,=\,\, the fuel price per gallon, etc..

OK - its a lame example right now, and we can refine it later. Some costs are buried in our averages. In trying for a comparison, we must try to approach like-for-like. The kW expended by a Jeremy Clarkson ( Er.. Ref: Top Gear - a questionable UK TV show) in seconds does not deliver the distance it might if he was not attempting comedy. A low-slung aerodynamic 20mph solar-powered death trap carrying a kings ransom in high-tech batterys and with tyres that will bio-degrade into fertilizer is not going to have the utility I need. I try to imagine my car, with all the space and features untouched - but gone electric!

This gets harder to reconcile

 

[GTrax]

Arrgh
I have no idea why it posted before I finished it. I did't see it happen.
Please help Mr. Moderator, and lose the part-finished posting

 

[OmCheeto]

A low-slung aerodynamic 20mph solar-powered death trap carrying a kings ransom in high-tech batterys and with tyres that will bio-degrade into fertilizer is not going to have the utility I need. I try to imagine my car, with all the space and features untouched - but gone electric!

This gets harder to reconcile

Yes. They had several "death traps" at the exhibit: 1 motorcycle, 2 scooters, 1 bike, 1 aero shrouded recumbent, and several 3 wheelers.

I didn't realize it until yesterday that Patrick's S10-EV was a sibling of the EV-1.
60 of the all electric S10's were sold, and hence, not crushed.

Anyways, the show was too much of a success as I was not able to interrogate all of the owners as much as I had wanted. The numbers for the non-death trap vehicles ran from 60 to 240mpg equivalent, @$4/gal. The 60 mpg number is probably too low as the owner stated that he used a 48vdc charger "capable" of 40 amps, charging for 7 hours, yielding a 20 mile range at 32mph. The actual charge rate was probably much lower, and hence, the mpg was probably much higher. The owner also gave me a "why on Earth would anyone ask such a question" look. He said he has driven it daily for the past 6 years.


Cost's were difficult to pin down as some owners were professional EV modifiers and others were just hobbyists.

There were several apples to apples comparisons at the show, but I'll chose the co-chairman's 1975 Porsche 914.
190 mpg at 20 mph
200 mpg at 60 mph(don't ask me, you run the http://www.evalbum.com/1137")
range ~ 60 miles
curb weight: 900 lbs more than original(pbso4 batteries)
top speed 80 mph

There were faster EV's: The street legal http://picasaweb.google.com/patrick0101/2008OEVAEVAwarenessDay/photo#5219760695742855122" tops out at 120mph. It's sibling, the White Zombie, was not in attendance, does zero to sixty mph in 2.9 seconds.

So my answer to the OP is; you get what you pay for. You can buy a Tesla for $100,000, a Zap for $10,000, or build your own for between $5,000 and $1,000,000 and have whatever you want.

 

[Gambler]

Regarding operating cost between electricity and gasoline, what about a different approach ... looking at the cost of energy needed to propel the vehicle.

At 132 megajoules of energy per gallon of gasoline at $4.00/gallon, the cost would be $0.03/megajoules.

At $0.09/kWh of residential electricity (average in USA, not off-peak) and 3.6 megajoules per kWh, the cost would be $0.025/megajoules.

If this is correct, the difference is not so great.

For a real example, if your trip to work is 35 miles per day in a gasoline vehicle that gets 35 mpg, your daily consumption of gas would be 1 gallon and the energy in that one gallon used is 132 megajoules and at $4.00/gallon, that would be a cost of $0.114/mile.

With a plugin electric car of identical physical features (aerodynamics, weight, etc to make the comparison accurate) and also getting 35 mpg, the same trip would consume the same energy - 132 megajoules. With 3.6 megajoules per kWh, the energy would be 36.67kWh and at $0.09/kWh, the total trip cost would be $3.30 or $0.094/mile.

If this exercise is done correctly, the savings of using residential electricity are not as much afterall.

Is this exercise flawed?

 

[OmCheeto]

Regarding operating cost between electricity and gasoline, what about a different approach ... looking at the cost of energy needed to propel the vehicle.

At 132 megajoules of energy per gallon of gasoline at $4.00/gallon, the cost would be $0.03/megajoules.

At $0.09/kWh of residential electricity (average in USA, not off-peak) and 3.6 megajoules per kWh, the cost would be $0.025/megajoules.

If this is correct, the difference is not so great.

For a real example, if your trip to work is 35 miles per day in a gasoline vehicle that gets 35 mpg, your daily consumption of gas would be 1 gallon and the energy in that one gallon used is 132 megajoules and at $4.00/gallon, that would be a cost of $0.114/mile.

With a plugin electric car of identical physical features (aerodynamics, weight, etc to make the comparison accurate) and also getting 35 mpg, the same trip would consume the same energy - 132 megajoules. With 3.6 megajoules per kWh, the energy would be 36.67kWh and at $0.09/kWh, the total trip cost would be $3.30 or $0.094/mile.

If this exercise is done correctly, the savings of using residential electricity are not as much afterall.

Is this exercise flawed?

Yes, your exercise must be flawed.

See post 1 and 2 of this thread.
Wordsmiths calculations were correct.
russ waters confirmed it.

The other 36 posts were, well, what I would call a butterfly effect, and can effectively be ignored in the context of your problem.

 

[Phrak]

Regarding operating cost between electricity and gasoline, what about a different approach ... looking at the cost of energy needed to propel the vehicle.

At 132 megajoules of energy per gallon of gasoline at $4.00/gallon, the cost would be $0.03/megajoules.

At $0.09/kWh of residential electricity (average in USA, not off-peak) and 3.6 megajoules per kWh, the cost would be $0.025/megajoules.[/qoute]

You'll have charging energy lost as heat in both the voltage conversion and battery itself. I figure 15% is reasonable. Boost your 25 cents to 28.7 cents.

If this is correct, the difference is not so great.

For a real example, if your trip to work is 35 miles per day in a gasoline vehicle that gets 35 mpg, your daily consumption of gas would be 1 gallon and the energy in that one gallon used is 132 megajoules and at $4.00/gallon, that would be a cost of $0.114/mile.

That's what I get.

With a plugin electric car of identical physical features (aerodynamics, weight, etc to make the comparison accurate) and also getting 35 mpg, the same trip would consume the same energy - 132 megajoules. With 3.6 megajoules per kWh, the energy would be 36.67kWh and at $0.09/kWh, the total trip cost would be $3.30 or $0.094/mile.

I get that number from your data too.

If this exercise is done correctly, the savings of using residential electricity are not as much afterall.

Is this exercise flawed?

Only partially. The energy of the gasoline is much more ineffiently applied in converting from gasoline to the drive axle of the car. Maybe 25% efficient. Electricity from the battery is much more effiently utilized. From the battery, assume 80% efficiency under EPA driving conditions, maybe. I've already assumed 85% efficiency in charging the batteries. 85%*80% = 68% overall efficiency from electric meter to drive axle.

68% to 25% is an efficiency ratio of 2.7 to one. Reduce your estimated cost of electricity by a factor of 2.7.

Better refinement of these two efficiency factors is actually what I lack for a decent comparison.

 

[Gambler]

Thanks for the replies guys!

Yes, your exercise must be flawed.

See post 1 and 2 of this thread.
Wordsmiths calculations were correct.
russ waters confirmed it.

OmCheeto, I was quite sure I was making a fundamental mistake OR that I over-simplified my comparison. But before making an investment, I'd really like to be SURE of the financial beneifits so I can 'fairly accurately' calculate the breakeven point especially if the breakeven point is beyond the life of a new EV or Hybrid ! For that reason, I would like to see and be comfortable with all the data and figures. For example ...

Just for sake of example, I have read that steady-state 50 MPH driving uses 40 HP

Probably Wordsmith read from a reputable source but again, before making an investment, I'd like to have something more firm.

The energy of the gasoline is much more ineffiently applied in converting from gasoline to the drive axle of the car. Maybe 25% efficient. Electricity from the battery is much more effiently utilized.

Well duh! Thanks Phrak! I think you made the flaw in my reasoning very clear - efficiency factor differences between the 2 types of propulsion.

So, for a car to go 35 miles on 1 gallon, you certainly paid for 132 megajoules but only 33 (132 x 25%) was actually transferred to the axle.

To compare with an electric car of same characteristics, the 33 megajoules transferred to the axle would be 38.8 (33 / 80%) consumed from the battery and 45.7 (38.8 / 85%) that was consumed from the residential electrical source (noting your battery charging efficiency).

In this case, gasoline is not 21% higher ($4.00/$3.30=1.21) than electricity but 250% higher ($4.00/(45.7/3.6*0.09)=3.50). Make sense?

And in terms of cost per mile:

Gasoline: $4.00/g / 35 mpg = $0.114 / mile
Electricity: $0.114 / 3.5 = $0.03 / mile

So in terms of cost per gallon of gas equivalent, electricity is:

$4.00 / 3.5 = $1.14

So, now the figures begin to look like those published by many promoters of the EVs.

Thanks Phrak!

Note: I spoke to a Mechanical Engineer friend who confirmed your 25% figure of car efficiency. He was not completely sure of the factors for electric motor by batteries but guessed 70% which is exactly what you stated (80% x 85% = 68%).

 

[Phrak]

I think your numbers could be right. I am not quit following them. What do you get if the efficiency is 70% from battery to axle?

 

[mheslep]

30 kwh (ref: Wordsmiths baseline energy requirement)
...
3500 weight of pb batteries
...



lithium ion (ref: http://en.wikipedia.org/wiki/Lithium_ion_battery )
...
187.5 kg (or 400 lbs) required
...

It is not meaningful to compare lead acid and Li ion in this way as these two cases must be two entirely different vehicles. The 3500lbs Pb batteries must be carried in a light truck or better, which then requires much more energy storage to perform similarly, requiring more batteries, more weight and so on. Thus you can quickly see Pb is not feasible for any reasonable multi-passenger vehicle capable of highway speeds, regardless of cost.

 

[mheslep]

Hello All,

I'm trying to get a sense of the cost of using electricity e.g., plug-in hybrid vs. the cost of operating the same vehicle using gasoline. I've read a comparison using the btu value of gasoline vs watts/btu but I'm not sold on that idea since the vast majority of thermal energy in an automobile goes out the tailpipe. What I was thinking of was choosing a 'standard' car like a Ford Taurus, operated on a highway at a steady state for one hour. Using horsepower as the common denominator between gasoline and electricity As far as gasoline consumption, I would propose dividing the miles traveled in the hour by some reasonable highway MPG. Just for sake of example, I have read that steady-state 50 MPH driving uses 40 HP. Figuring 25 MPG highway, gasoline at $4.00/gal and electricity (746 W/hp * 40 hp. for one hour = 29.84 KWH. At $0.10/KWH, driving the 50 miles cost $2.98 using electricity or 2 gallons of gas = $8.00.

Obviously, the example is greatly simplified, but is it a fair comparison?
Thanks for your thoughts.
Wordsmith

The HP load for level cruising depends of course of the aerodynamics of the vehicle, but the average sedan cruising at 60mph requires more like only 30HP (22.38kW) to overcome air drag and rolling resistance, a bit less for aerodynamic sports cars.
http://mb-soft.com/public/headlite.html
Then the electric drive train efficiency of motor + battery is ~85% efficient. Thus 22.3kWhrs/0.85=26kWh must be stored in the batteries for the hour trip. Charging them before you go loses 10%, so one has to buy roughly 29kWhrs of energy to drive the 60 miles. That compares closely with published numbers of the upcoming Chevy Volt PHEV: 16kWh max charge on which it will travel 40 miles.

That is still $2.9 for 60 miles, though overnight power is typically cheaper ($0.06/kWh here) so perhaps $1.7 for 60 miles, vs $9.6 for 2.4 gallons of $4gal/gas. In the narrow case where one makes nothing but short battery only trips for a 10,000 mile year one saves $1316/year over 25mpg gasoline powered travel, best case.

Some other considerations for weighing that possible cost savings:
o Plug-in hybrid $5000 to $15000 additional cost vs comparable gasoline vehicle, given the current battery costs.
o Gasoline might go much higher, or their may even be 1970's like fuel shortages in the 10 year life of the car, in which case an PHEV would be very handy.
o Gasoline might go much lower (EIA/DoE currently predicts below $3/gallon again by 2015, in 2008 dollars)

 

[Gambler]

I think your numbers could be right. I am not quit following them. What do you get if the efficiency is 70% from battery to axle?

It is a given that for a car of 35 mpg, the energy from the gasoline used to go 35 miles is 132 megajoules. Considering an efficiency of 25% (your figure), 33 megajoules were actually applied to the axle. So, for the same car in the same conditions going the same 35 miles, 33 megajoules would be applied to the axle from an electric motor drive system. If the efficiency "from battery to axle" is 70%, then 47.1 megajoules was consumed from the battery (33/.70). If your other figure of 85% in charging the battery is correct, the energy used from the plugin source would be 55.5 (47.1/.85).

Anyway, you put me on the right track in including the efficiencies of the different drive systems - gasoline & electric - which are very significant. Only now do I begin to understand the advantage of using an EV over gasoline cars.

 

[Phrak]

Gambler-

I didn't see what you were doing the first time. You're going down from gasoline to axle on one car and up from axle to electric meter on the electric. Brilliant.

 

[Gambler]

Exactly. I think it simplifies the comparison. The only challenge is to accurately determine the efficiencies for a vehicle of interest.

 

[WhoWee]

It looks as though it's time to dust this thread off again - with gasoline hovering around $4.00 per gallon?

 

[wavering]

I spent a bit of time doing an analysis BEFORE I found this thread, this is what I came up wth:

According to Wikipedia, the best power stations convert fuel to power at 60% efficiency whereas a car is nearer 40% efficiency. But of course, there are further losses from the power station to the wheels of your electric car. In summary losses are:

Power Staion losses = 40%
Transmission losses = 7%
Transformer/rectifier losses = 4%
Battery charge losses = 10%
Battery dis-charge losses = 10%
Electric motor losses = 10%

So if you start off with 100 units of fuel at the power station, you end up with about 39% at the wheels, as follows:
100 X 0.6 = 60
60 X 0.93 = 55.8
55.8 X 0.96 = 53.6
53.6 X 0.9 = 48.2
48.2 X 0.9 = 43.4
43.4 X 0.9 = 39.1

Whereas, if you have 100 units of fuel in your car you end up with 40% at the wheels

So, nothing in it really BUT the electric car has restricted range and what about the heating/cooling in extreme weather? If
the typical capapcity is 20KwH then a 2KW heater (cars are very badly insulated since in a petrol/diesel car, heat is a waste
product) could knock a further 10% off reducing the output available from 39 units to nearer 35

Also, if your car is not used the battery can lose 8% of its power per month just sitting there

As I see it, the key advantages of the elctric car is that it appeals to arts graduates who think it is pollution free and
it also appears very cheap in comparision to petrol/diesel because fuel at pumps (in most countries) is very heavily taxed
whereas electricity is (currently) untaxed.

All numbers form web searching. Any observations very welcome - I am not trying to score points (apart from over arts graduates who write in the media without any understanding of physics), just clarify it in my own mind.
Bob aka wavering
.

 

[WhoWee]

I spent a bit of time doing an analysis BEFORE I found this thread, this is what I came up wth:

According to Wikipedia, the best power stations convert fuel to power at 60% efficiency whereas a car is nearer 40% efficiency. But of course, there are further losses from the power station to the wheels of your electric car. In summary losses are:

Power Staion losses = 40%
Transmission losses = 7%
Transformer/rectifier losses = 4%
Battery charge losses = 10%
Battery dis-charge losses = 10%
Electric motor losses = 10%

So if you start off with 100 units of fuel at the power station, you end up with about 39% at the wheels, as follows:
100 X 0.6 = 60
60 X 0.93 = 55.8
55.8 X 0.96 = 53.6
53.6 X 0.9 = 48.2
48.2 X 0.9 = 43.4
43.4 X 0.9 = 39.1

Whereas, if you have 100 units of fuel in your car you end up with 40% at the wheels

So, nothing in it really BUT the electric car has restricted range and what about the heating/cooling in extreme weather? If
the typical capapcity is 20KwH then a 2KW heater (cars are very badly insulated since in a petrol/diesel car, heat is a waste
product) could knock a further 10% off reducing the output available from 39 units to nearer 35

Also, if your car is not used the battery can lose 8% of its power per month just sitting there

As I see it, the key advantages of the elctric car is that it appeals to arts graduates who think it is pollution free and
it also appears very cheap in comparision to petrol/diesel because fuel at pumps (in most countries) is very heavily taxed
whereas electricity is (currently) untaxed.

All numbers form web searching. Any observations very welcome - I am not trying to score points (apart from over arts graduates who write in the media without any understanding of physics), just clarify it in my own mind.
Bob aka wavering
.

Is the plant coal burning?

 

[whocouldshebe]

I'm going to get a gas generator and use that to charge up my electric car to save gas! LOL Obviously a gallon of gas produces more power than a battery can collect from a gallon of gas. Any time you charge a battery you lose at least 60% of the electricity to heat and charge dissipation into the air around the terminals. You fail to consider this in price calculations. Just because a battery hold X number of KWH doesn't mean that's all you will get charged for. It costs you at least 3 TIMES X number of KWH to charge up the battery.

Gasoline engines are already extremely efficient at converting tiny gas explosions into physical movement. If we could just turn pistons off when the force isn't needed, the engine completely off when idle, lower weight, shrink the size, etc. then gas engines would murder the electric car industry on cost savings alone!

They do all this for electric vehicles, but not on gas cars, since there is no reason to conserve energy, there is an abundance already wasted, you could power a home from a single gas engine for hours off of a gallon of gas, plenty of amps there, then try and do that with an electric car battery, it'll pucker out in just a couple minutes.

All your comparisons are apples to oranges, I mean think about my first comparison, I could just as easily use a gallon of gas in a generator to charge 5 cars for an hour, then go drive each car for an hour off that same charge. Only crazies would say a battery stored charge is the best way to get electricity, when we just wasted enough electricity to power up 15 cars because of the 60% loss we trashed to charge up the 5 cars using a gas powered generator. Even solar is nutz, 60% loss at the panel, then another 60% loss to charge, just to charge up a AA battery. It would be tons more efficient to just use an ounce of gas in a tiny engine to get the instant power of 8 AA batteries with nearly 90% efficiency.

We should be working on smaller gas engines with higher efficiencies and ways to produce gas quickly instead of promoting tons of wasteful storage technologies. Yeah batteries are great, but only to store an excess charge that would otherwise be lost, but other than that, the answer is simple, if you don't need 100% of that energy NOW the turn it OFF NOW.

GAS ENGINES SHOULD TURN OFF WHEN THE ENGINE IS AT REST! EXTRA PISTONS SHOULD SHUT DOWN WHEN HORSE POWER IS NOT NEEDED! We don't need 6-8-10-12 cylinders unless for a light load. 2-4 is more than enough power to move 1 person from point A to point B at 200 MPH or better. Look at motorcycles and scooters, 80-120 mpg, the same engine could still move 4 people the same distance, just at lower acceleration/hp. The way engine power technologies is moving today is completely ridiculous.

 

[mheslep]

I spent a bit of time doing an analysis BEFORE I found this thread, this is what I came up wth:

According to Wikipedia, the best power stations convert fuel to power at 60% efficiency whereas a car is nearer 40% efficiency.

First, electric power plant conversion from fuel to electricity tops out at ~45%. The additional 20% refers to the use of the rejected waste heat for buildings or industrial processes. Second, most cars on the road today, that is, conventional spark ignition + gasoline cars, are closer to 25% efficient, tank to wheels. http://cta.ornl.gov/TRBenergy/trb_documents/an_assessing_tank.pdf" , as reported by GM the Chevy Silverado has a tank to wheels efficiency of 17%, well-to-wheels efficiency of 14%.

But of course, there are further losses from the power station to the wheels of your electric car. In summary losses are:

Power Staion losses = 40%
Transmission losses = 7%
Transformer/rectifier losses = 4%
Battery charge losses = 10%
Battery dis-charge losses = 10%
Electric motor losses = 10%

So if you start off with 100 units of fuel at the power station, you end up with about 39% at the wheels, as follows:
100 X 0.6 = 60
60 X 0.93 = 55.8
55.8 X 0.96 = 53.6
53.6 X 0.9 = 48.2
48.2 X 0.9 = 43.4
43.4 X 0.9 = 39.1

I'd have to check, but I believe the '7% transmission' losses, a commonly cited figure, includes transformer losses.

So, nothing in it really BUT the electric car has restricted range and what about the heating/cooling in extreme weather? If
the typical capapcity is 20KwH then a 2KW heater (cars are very badly insulated since in a petrol/diesel car, heat is a waste
product) could knock a further 10% off reducing the output available from 39 units to nearer 35

Yes, but 1) the maximum of 2KW for heat would only be used for a few minutes to knock the chill off the passenger compartment and fall rapidly afterward, 2) waste heat from the battery and motor can also be used to heat the passenger compartment.

Also, if your car is not used the battery can lose 8% of its power per month just sitting there

As I see it, the key advantages of the elctric car is that it appeals to arts graduates who think it is pollution free and
it also appears very cheap in comparision to petrol/diesel because fuel at pumps (in most countries) is very heavily taxed
whereas electricity is (currently) untaxed.

All numbers form web searching. Any observations very welcome - I am not trying to score points (apart from over arts graduates who write in the media without any understanding of physics), just clarify it in my own mind.
Bob aka wavering
.

Above you are essentially comparing well-to-wheels (as in natural gas/oil well) efficiency for electric vehicles to tank-to-wheels (vehicle fuel tank) for a gasoline powered vehicle. Gasoline also incurs losses getting to the vehicle: distribution via pipeline and then tanker truck, during which time there's spillage, http://www.nytimes.com/1988/05/10/us/gasoline-evaporation-termed-a-pollution-factor.html" , etc.

Returning to the subject topic for a moment, the cost of driving, not efficiency, with respect to fuel costs alone one will pay three times more for gasoline per mile than for electricity in an electric car. With respect to maintenance, some http://online.wsj.com/article/SB10001424052748704584804575644773552573304.html" The remaining question is the cost of battery replacement - how long will it last, cost, etc.