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Calculating ACTUAL electricity cost to drive

Discussion in 'Model S: Battery & Charging' started by jeffdom1978, Jul 4, 2018.

  1. jeffdom1978

    jeffdom1978 Member

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    Hi guys,

    I am trying to calculate or get as close to I can on how much it costs me to charge my car. Going to see a bunch of family today and wanted to show them the savings!

    From my understanding, to calculate cost to fully charge your vehicle, you get your electric bill, multiply the cost per kWh X your battery pack's capacity, so mine is 75.

    I just hit 1,000 miles and if this above estimate is correct, my cost per Kwh is .0735 X 75 = $5.51 to fully charge it.

    What I'm confused about on my Utility bill, I just want to calculate from the "Supply" part, right? Do I need to add anything from the Delivery section? See my bill below... Are my calculations correct?

    Also, to calculate total monthly cost to drive the car, I use the Remote S app on my phone and it gives an "Estimated" miles when the car is fully charged based on driving habits.

    90% charge says:
    Ideal: 280
    Rated: 226
    Estimated: 190

    Whats the math now? thanks!

    IMG_0861.jpg
     
  2. ItsNotAboutTheMoney

    ItsNotAboutTheMoney Well-Known Member

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    You have to add _all_ the per-kWh numbers:
    0.06030
    0.01328
    0.03174
    0.00121
    0.00033
    0.00189
    0.00195
    0.00015
    Total is:
    $0.11085/kWh

    Plus, I think the Illinois state tax varies, with some costs per kWh and some costs fixed.
    To simplify if you take that state tax line and divide over your 2,222kWh you get an extra $0.00329/kWh

    Total after tax is
    $0.11424/kWh
     
  3. DrizztVD

    DrizztVD Member

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    You'd want to calculate the cost per km/mile, ideally. 190 miles on (75*0.9 = 67.5 kwh). That gives 67.5/190 -> 355 wh per mile in your case. Your full bill is rather detailed, but it would be best to separate fixed and variable costs -> 268.56 -10.84 - 4,63 = 253.09 variable costs -> 253.09 / 2222 kWh = 0.1139 $/kWh. That gives 0.1139 $/kWh * 0.355 kWh/m = 0.04043 Dollars per Mile

    We can work directly with the variable cost value because the overheads can be said to accrue to your house only - although slightly contentious on the long term, this will be true for the next couple of years.

    Taking a stistically significant measurement for the Camry 2018 Toyota Camry MPG - Actual MPG from 5,834 Toyota Camry owners shows 33.4 MPG. That gives us, at US average gas price of $2.54/gallon -> 2.54 $PG/33.4 MPG = 0.07605 Dollars per Mile

    Therefore, it costs you $7.682 to recharge 190 miles worth of range.
    Compared to $14.45 to refill fuel in a Camry to drive 190 miles.
     
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  4. MyJoule

    MyJoule Member

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    I'm not sure about the S75D, but my S85 takes ~ 330WH to add 1 mile of range to the range meter vs it uses ~t 302WH/mile over the lifetime of usage ( I think Tesla rates the usage as 290WH/mile for the range meter, so I'll use that to calculate the costs) ( I have a bit of a lead foot.:) ) In my case: 330/290= 1.13 or 13% lost due to efficiency of the charging hardware and other losses.

    We never can use 100% of the battery (WK057 has shown that in another thread) I think I have ~ 75KWH still in my battery after 45000 miles. (my 90% charge is 233 miles still) So adding 67KWH ( 0% to 90%) would take 13% more or ~76KWH to charge 67KWH into the battery Our power is roughly .12/KWH so just over $9 for a fill up (76 x .12=9.12) + taxes of course.
     
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  5. SSedan

    SSedan Member

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    Are you talking a fair weather trip or do you want to know cost at end of year?

    The car will use a lot of energy when plugged in that never charges the battery partiularly in winter. There are energy losses in charging too.

    Up near Green Bay the Tesla caused a much bigger than expected jump in electric bill in large part because of the winter battery warming.
    Still happy just urging caution in your calculations and hopes.
     
    • Like x 1
  6. DrizztVD

    DrizztVD Member

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    For the sake of completeness, it is necessary to add maintenance costs in to the comparison. The problem is that mainenance costs for EVs are not known, because you need to get actual data for 10 year old EVs before you can compare them. The expectation is that oil and servicing will costs will be about a third of the cost of a gas vehicle. In addition, the battery degradation may, especially in the case of a Nissan leaf, add substantially to the cost per mile. We're talking $6000 for a new battery over 100 000 or 200 000 miles = 0.03-0.06 Dollars per Mile

    The long and the short of it is, DO NOT BUY a brand who's battery is likely to fail just after warranty. Tesla batteries appear to be able to do 300 000 miles+ - which is a much better proposition.
     
  7. DrizztVD

    DrizztVD Member

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    Offset by maintenance savings likely. Can you provide numbers for maintenance?
     
  8. DrizztVD

    DrizztVD Member

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    Battery warming or phantom drain? Phantom drain is because Li-ion batteries discharge spontaneously inside the cells. Having a colder battery is actually better for reducing this behaviour - aka you could save money by parking your EV outside instead of in the garage in winter. (theoretically)
     
  9. SSedan

    SSedan Member

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    Brought my car in for service at 65k miles shortly after buying it. $1100 $800 for 4year annual based on mileage and $300 to swap a malfunctioning primary charger to secondary rather than pay $2200 to replace.

    Never had another vehicle need so much money in repairs or service so new.
    The "zero maintenance cost" is a lie people here tell themselves and the world.

    2-3 oil changes a year on an ICE is what $100, let's pretend engine air filters are annual and in dusty places may be and call that another $50.
    Transmissions are 100k or lifetime fill anymore, sparkplugs are 100k and often neglected and still function.
    Tesla eats tires more than most ICE due to weight and torque let is add that to driving costs.

    I love the car but feel most here are dishonest to themselves about cost of ownership.
     
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  10. BlueRocket

    BlueRocket S90D HW2 MCU1 42.3

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    The usable capacity of the battery is 72.6 kWh (not 75): Tesla Motors: PLEASE stop lying about specifications (60 to 75 upgrade)
    Using your electricity cost of $0.11424/kWh it costs about $8.29 to "fill up". You can use the Camry numbers to compare or a more luxurious model that likely gets lower mpg or requires a higher and more expensive grade of gasoline.

    Your rated miles for a 100% charge is 251 miles so cost per mile is 0.0330 dollars per mile. The way I like to communicate my savings is in mile per gallon equivalents which for you (comparing to the Camry numbers) is about 77 mpg.
     
  11. Raechris

    Raechris Member

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    So you are not bringing hot dogs :)
    Absolutely! It is a cost to get the watts to your car like the cost to transport gas to the station.
    Your cost is 12c per kWh. Now to determine how much you consume. The 75 pack has 72.5 usable, meaning full is 65 kWh and you don’t go down to zero. Then there is HVAC, vampire and charging losses. I use TeslaFi for metrics but for ICEES they won’t get any of this - assume 250 watts per mile or 4 miles to kWh- therefore 3c per mile and round up to 5c for the other stuff. If they get 25mpg on 3 gas, they are at 12c per mile - point made.
     
  12. N..8

    N..8 Member

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    A little of topic but there really isn't any savings in buying / driving a Tesla over an ICE. It is way more efficient as some of the rough numbers above have shown it cost about 50% percent less per mile to drive. True-fully I'm not sure you could drive a Tesla for enough miles to hit the ROI before the maintenance/replacement cost become overwhelming. I drive it because I enjoy it, even when we get a bad Firmware update I'm sort of ok with that, give it a bit and another one will fix it. That's what I explain to people who ask me about it.
     
  13. Big Dog

    Big Dog Member

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    I'm assuming that you have never owned a high-end Euro car: Jag, Bimmer, Mercedes? My '01 Jaguar S-Type with 66,000 miles on it needs bushings all around. Add in other parts which might as well be swapped out while its pulled apart (control arms), and the dealer quoted $2500/wheel. Fuel injectors fail every 3-4 years. (known design flaw due to heat build up, $1500 part.) Best road car I've ever had, but mighty expensive to repair.

    Cant wait for my second M3.
     
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  14. jeffdom1978

    jeffdom1978 Member

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    Thanks for all the great info! I figured this topic is debatable, I was just looking to figure out how much less a month I would pay in energy costs versus my previous Lexus. So just taking into account basic energy numbers, Lexus I spent about $250 a month in gas (Premium) for 1,000 miles and Tesla will cost around $47 a month at .11 kWh plus battery maintenance/AC which I'll offset by the free supercharging I've done.

    Sound about right?
     
  15. ItsNotAboutTheMoney

    ItsNotAboutTheMoney Well-Known Member

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    $0.114/kWh maybe with tax.

    You'll also need to add vampire losses

    Also, you don't use the whole capacity of the battery, you would need the usable portion

    <cost_of_fuel_per_month> =
    <paid_miles_driven_per_month> / <kwh_per_mile_from_battery_to_wheel> / <charging_efficiency>
    x <net_price_per_kwh>
    + <vampire_loss_kwh_per_day> x <net_price_per_kwh> x ( 365.25/ 12 )


    For <kwh_per_mile_from_battery_to_wheel> / <charging_efficiency> you could just throw in the EPA rating and fudge it.
     
  16. ewoodrick

    ewoodrick Active Member

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    I had a car in which some idiot cross-threaded the spark plugs when replacing. Yep, that was more than $2200. There's a lot of ICE vehicles in which a simple computer failure tends to cost that much.

    I CAN say that the cost of maintenance on a 3.5 year 2015 Leaf lease was $0. No oil, no tires, 94% on battery. ZERO Dollars.

    I'm not sure how I can be any more honest than that. Crap, I just remembered, I lied. I paid for car washes.
     
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  17. AviP

    AviP Member

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    One of my ICE vehicles is 10 years old and I just spent $3500 to upgrade brakes, U-joints and tie-rods. But it is as good as new now. I don't think a BEV is about savings, it's about the environment and cool factor. I don't care for AP. I plan to go see a M3 in person and will cancel/continue based on that. I'm a 03/31 line waiter for an SR AWD.

    If you seek an economical vehicle, a Prius might arguably be cheaper than a M3 SR from total cost of ownership perspective.
     
  18. Big Dog

    Big Dog Member

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    Move to California (where the costs are $0.25/kWH) and you'll save even more!
     
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