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Tesla's "How Much Can I Save" Page Ignores Charging Losses

Discussion in 'Model S: Battery & Charging' started by smorgasbord, Feb 1, 2013.

  1. smorgasbord

    smorgasbord Active Member

    Jun 3, 2011
    SF Bay Area

    This cost calculator ignores all charging losses. Verify that for yourself by setting the cost per kWh to $0.10, set miles per year to 10K - see that your total cost is $283. Then read the 283Wh/mile disclaimer at the bottom.

    The EPA, on the other hand, reports 380Wh/mile on the sticker, yet gets 265 miles of range. Assuming Range mode is 95% of 85kWh, that's 265 miles on 80.75kWh, or 305Wh/mile.

    The difference, 75Wh/mile is all charging losses.

    Now, I suspect that one reason this is so high is that charging in Range mode forces extra battery cooling, which consumes power. Does anyone know what the penalty is when charging in Standard mode? I might guess the loss is under 50Wh/mile - but does anyone have a dedicated meter or done something with a ChargePoint to know for sure?

    At any rate, Tesla really should be more honest about the costs. After all, even though it's 25% more power needed, that's only about a penny per mile.
  2. ModelS1079

    ModelS1079 Member

    Jun 23, 2012
    Suburban Boston
    Really interesting. And cold weather takes the efficiency down another notch. Still a great fuel value, but I agree it all has to be above board in regards to total cost/mile driven in regards to charging, and then TCO overall.
  3. Objective1

    Objective1 Member

    Dec 29, 2012
    Albany, NY, USA
    I agree with smorgasbord "Tesla really should be more honest about the costs."

    This is one big area where people have underestimated the costs of operating a Model S (cold weather performance is another).

    Objective estimates of cost and real-world range are the key to encouraging widespread acceptance of EVs and avoiding a backlash from disappointed early adopters.
  4. Doug_G

    Doug_G Lead Moderator

    Apr 2, 2010
    Ottawa, Canada
    On the other hand, ICE don't manufacturers say anything about their fuel economy in cold conditions. I doubt you can get figures for this. If Tesla wanted to talk about cold weather effects on efficiency they'd have to come up with comparison figures for ICE vehicles, which might be hard to come up with.

    - - - Updated - - -

    On this point, how often do you get the EPA mileage on your gas car.

    The fact is, "mileage may vary". It's hard to be precise about these things because there are so many variables.
  5. tezco

    tezco Sig P85

    Nov 9, 2012
    There are also significant idle power losses, euphemistically referred to as the "vampire load" (of the always on electronics, which I'm finding range from about 4 to 5 kWh per 24 hours.) This represents the daily top-off charge needed, as measured at the wall).....

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