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Is an electric car still cheaper to drive with gasoline at $2/gallon?

Discussion in 'Electric Vehicles' started by ToddRLockwood, Jan 19, 2015.

  1. ToddRLockwood

    ToddRLockwood Active Member

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    Is an electric car still cheaper to drive with gasoline at $2/gallon?

    First, it's important to compare apples-to-apples. A fair comparison to my 2013 Tesla Model S Performance would be an Audi S8 in terms of price, performance and vehicle weight. Audi lists an EPA average of 20mpg for the 2015 S8.

    Here's how they compare...

    At $2.50/gallon (rock bottom price for premium gasoline required for the Audi S8), it would cost $125 to go 1,000 miles in the Audi.
    I've driven my Tesla 30,000 miles, through two Vermont winters, and I used an average of 365 watt/hours of energy per mile. So for each 1,000 miles, I consumed 365kWh of energy. At the U.S. average electric rate of $0.12 per kWh, it cost $43.80 to go 1,000 miles in the Tesla.

    When gasoline prices come back to their previous levels, and they will, the Tesla will be five times less expensive to fuel than the Audi.



    Audi-TeslaFuelCostComparison.jpg
     
  2. deonb

    deonb Active Member

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    It's not really apples to apples yet if you compare real world usage of the Tesla with EPA rating of the Audi.

    You should compare EPA of both.

    However, 365kWh of battery consumption will require far more than that to charge, due to various losses. You'll likely need more than 450 kWh from the wall.


    I think if you use EPA on the one hand and account for losses on the other things will probably even out, but it would be nice to have the correct numbers before a reporter picks this thread up and run with it.
     
  3. nwdiver

    nwdiver Active Member

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    There are a lot of factors to consider here... there's also the solar PV aspect. I over produce by ~50% and I only get paid ~$0.03/kWh for my excess generation so driving an EV is MUCH cheaper for me.

    Even if you consider the average; PV costs are now <$1.50/w for all equipment. For most of the country that's a 20 year average cost of $0.045/kWh.

    EV consumption is also different from other forms of electric consumption in that you have significantly more control over when you charge your car. You can get paid to give your utility control over when your car starts/stops charging due to changes in supply/demand on the grid... doing that to the rest of your home would likely be mildly inconvenient.
     
  4. ScepticMatt

    ScepticMatt Member

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    MPGe and other EPA numbers include losses:

    All-Electric Vehicles
     
  5. ZBB

    ZBB Emperor

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    Quick answer: Yes

    Prior to getting the Tesla, I tracked my MPG and gas costs on my 2 prior cars, both of which averaged 22-23 MPG. Over about 5 years, I averaged ~13k miles per year, which cost just under $200 for gas each month, at an average ~$3.50 per gallon. At $2/gallon, the cost would have been ~$110/month to buy gas.

    I've had the Tesla for 19.5 months now, with just over 30k miles. About 5k miles were powered by Superchargers, at a fuel cost of $0. I've had another ~$30 of public paid charging (1/2 of which was at Disneyland...), and the rest of the charging was done at home, where I charge at night and pay slightly under 7 cents/kWh. Average cost each month in 2014 was estimated at ~$30 (based on my monthly car stat summary, adjusted for charging losses at 15%).

    So $30/month to power the Tesla vs $110/month for an ICE @ $2/gallon...
     
  6. ToddRLockwood

    ToddRLockwood Active Member

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    Interesting thoughts. By using the EPA estimate of 20MPG on the Audi side, I thought I was giving the Audi a leg-up. Those estimates are usually optimistic. I could base the Tesla consumption on the EPA estimate of 89MPGe. That would look something like this...

    1000mi / 89MPGe = 11.24 gal gasoline equivalent

    11.24 x 33.7kWh* = 379kWh

    379kWh x $0.12** = $45.48

    *Amount of energy in a gallon of gasoline according to EPA
    ** U.S. Average Electric Rate (2013)

    I agree that I probably should add in a typical 15% charging loss. I've seen that number mentioned on TMC. Does anyone have a real number?
     
  7. abasile

    abasile Independent Software Eng.

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    The EPA MPGe figures already account for charging losses.
     
  8. thefortunes

    thefortunes Member

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    It would depend on how you charge (amperage, voltage, ambient temperature, etc...).

    I have tracked my charging data for the 33k miles I have had my Roadster and it varies from 20%-30%. Overall I am at 24%.
     
  9. ToddRLockwood

    ToddRLockwood Active Member

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    So do you think my previous post has is right then, using MPGe?
     
  10. thefortunes

    thefortunes Member

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    I would be very curious to see your reference for this, as charging losses are variable depending on the items I noted above.

    As I understand it, MPGe is calculated based on the amount of energy (115,000 BTU) in one gallon of gas which equates to 33.7kWh of electricity. The distance you can drive on 33.7kWh is your MPGe and does not factor in charging losses.

    Edited to add:

    From Electric Vehicles - Learn More About the New Label | Fuel Economy and Environment Labels | US EPA

    For those vehicles that do not use liquid fuels--such as electric vehicles, plug-in hybrid electric vehicles operating on electricity, and compressed natural gas vehicles-- the labels display miles per gallon of gasoline-equivalent (MPGe). Think of this as being similar to MPG, but instead of presenting miles per gallon of the vehicle’s fuel type, it represents the number of miles the vehicle can go using a quantity of fuel with the same energy content as a gallon of gasoline.
     
  11. Saghost

    Saghost Active Member

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    I thought they told you in the same page you're quoting, but it doesn't look like they do. A little quick math will prove it must have charging losses, though:

    The same EPA sticker gives 265 miles range and 38 kWh/100 miles for the same blended conditions, right? That means the at the point of measurement, the "85 kWh" Model S must have used (265/100*38=) 100.7 kWh of power.

    You'll find the same thing for all of the other EVs and PHEVs - the Volt's 35 kWh/100 miles and 38 miles implies 13.3 kWh used (actually about 11 available for use.)
    Walter
     
  12. thefortunes

    thefortunes Member

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    Interesting and thanks for that.

    I wonder how they calculate charging losses given their variability?
     
  13. Saghost

    Saghost Active Member

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    The same way they do everything else, I imagine - control the variables. :)

    The variability in losses isn't the charger randomly eating a larger percentage of the power one day than the next. Instead, it comes from the environment - outside temperatures, battery temperature, maximum charge rate from the EVSE. So if you get the car in the same situation, it should take the same predictable amount of energy. All they have to do is figure out what makes sense as a representative sample and specify those conditions for all of the testing.

    This isn't any different from anything else in EPA testing - they know that hundreds of factors affect real world fuel economy, so to build a standard for comparison they specify a set of conditions and driving profile to compare with. On good days it even bears some resemblance to the way some portion of the population drives...
    Walter
     
  14. ToddRLockwood

    ToddRLockwood Active Member

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    #14 ToddRLockwood, Jan 19, 2015
    Last edited: Jan 20, 2015
    So does this look correct then?

    Tesla Model S P85

    1000mi / 89MPGe[SUP]B [/SUP]= 11.24 equivalent gallons of gasoline

    11.24 x 33.7kWh[SUP]C [/SUP]= 379kWh
    379kWh x $0.12/kWh[SUP]D [/SUP]= $45.48
    1000mi = $45.48


    [SUP]B [/SUP]EPA estimate including charging losses
    [SUP]C [/SUP]EPA energy in a gallon of gasoline
    [SUP]D [/SUP]Average U.S. electric rate
     
  15. qwk

    qwk Model S P2681

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    Don't forget to add in the vampire load to the calculations. If you drive the car on a longer trip, it gets much better electron economy than short trips here and there(just like any other car). Charging the car on a 14-50 @40A, at $0.10 per kWh electricity cost, it costs right at $1 to get 30 rated miles. With the vamipre load in the winter, sometimes I can only go 15 real miles on 30 rated. That is only equivalent to a 30mpg vehicle with gasoline at $2 per gallon.
     
  16. roblab

    roblab Active Member

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    So, you don't think that a gas engine car takes a hit in mileage when it is cold? "All that waste heat" somehow gives it better mileage? I personally think that a gas car gets worse mileage when it's really cold, maybe not as much as an EV, but worse.

    I live in California, so I can't understand how your cold sucks all that mileage out of your Tesla, but I won't deny it. But I wonder how much is the heater, how much is "having" to go fast no matter what, etc., etc. This is not a good comparison. And Vampire Loads, at least here in California, are too small to worry about. It's the heater, and it's going fast. Or are those what you call "Vampire"? Other than that, it might be the cold. But not much, here.

    Even at 15 miles with your "Vampires", you are getting $2 per gal gasoline. BUT you are not getting a whole slew of negative stuff. When I compare my EV with a gas car, I am not just thinking about how many miles per gallon I get, nor how many dollars I pay for power. I wish others would catch on and see that not making a bunch of poison and dumping it into the air my grandkids breathe might be a good thing.
     
  17. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    It's not uncommon to lose 25% mpg in a gas car when it's very cold. However, most people don't know what they get because they never keep a logbook. It then comes a a big surprise when they get a car that tells them.
     
  18. David99

    David99 Active Member

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    Interesting! I actually don't care too much about the gas price being down in terms of how much I save. I bought the Tesla for many reasons. Saving on gas is a nice perk, but wasn't the most important reason. Buying a much cheaper car with a good mileage would have been a cheaper alternative for sure. For me it's mostly about avoiding oil. Everything about oil is a bad idea. From drilling, fighting wars over it, foreign dependency, global power battles, pollution, noisy engines.
    In a way the Tesla is much more of a car I ever wanted to pay for, but I believe in it on so many levels that I did it anyways.
     
  19. gregincal

    gregincal Active Member

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    It definitely includes charging losses. It's not the "distance you can drive on 33.7kWh", it's the distance the car drives after drawing 33.7kWh from the wall. It's not calculated, it's measured, so it's by far the easiest way to measure. Charge the car to capacity, do the EPA test cycle until the car stops, charge the car again measuring how much electricity it takes.
     
  20. qwk

    qwk Model S P2681

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    I'm not disagreeing with your points, but since an ICE creates lots of wasted heat, in the winter it becomes useful. The Model S doesn't create much heat from the motor, so the heater sucks a lot of power.

    The Model S is still a much more superior car, but with gas at $1.60 a gallon here, the savings aren't that much.

    - - - Updated - - -

    BTW, my vampire load can be as much as 20 rated miles PER 24 hours when its below 30* F. That is a lot of waste. That's like losing almost a gallon of gasoline per night.
     

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