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Energy usage in a 60kWh vs 85 kWh Model S

Discussion in 'Model S: Battery & Charging' started by StephRob, Feb 3, 2013.

  1. StephRob

    StephRob Member

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    My husband and I took a drive today to compare the energy usage of his P85 vs my 60. We took a 15.1 mile drive through mostly suburban streets, following the same route at the same speed - our own little Model S parade! The route was mostly reasonably flat except for the quite steep hill coming down from our house and coming back up the same hill at the end. We tried to control for all variables that we could (climate control off, windows closed, regen on, etc). My husband is about 60 pounds heavier than I am and he has the 21" wheels and I have the 19", so those were the main differences.

    In short, our results seem to validate differences in the EPA ranges. At the end of the 15.1 miles, total energy used for my 60 kWh S was 4.2 kWhs with an average of 276 watts per mile. Total energy used by the P85 kWh was 4.6 kWh and an average of 303 watts per mile. So the 65kWh car used only about 91% of the energy that the 85 kWh used to go the same distance at the same speed.
     
  2. ChadS

    ChadS Petroleum is for sissies

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    Thanks for trying this. So the 85 with 21's took about 10% more energy than the 60 with 19's.

    Tesla's latest calculator says the 21's cost about 6%. So that leaves 4% for weight difference (of drivers AND the cars), and any efficiency difference (the EPA makes the 60 sound more efficient than you'd expect from the weight difference; but it's not clear if there's really any driving efficiency gains - I would bet it's more likely in charging efficiency).
     
  3. StephRob

    StephRob Member

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    It makes me wonder whether the EPA did their ratings with a 85 kWh using the 21" and the 60 using the 19". It would seem like it.
     
  4. brianman

    brianman Burrito Founder

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    I'm almost willing to put money on that bet.
     
  5. StephRob

    StephRob Member

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    I would have thought that Tesla would have had the EPA use the 19" on the 85 kWh car and order to get the best range/energy usage rating possible. Seems like a bit of a mistake to evaluate a car with a $3500 option that hurts range.
     
  6. jerry33

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

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    Depends on your goal. If you want most people to be able to get the EPA mpg then you give them a conservative configuration. If you want to have a high number and get zillions of complaints about how the car doesn't get EPA...
     
  7. StephRob

    StephRob Member

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    True, but then you'd think they'd evaluate the 60 kWh with the 21"s too. :smile:
     
  8. brianman

    brianman Burrito Founder

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    Unless of course they didn't have an 19" wheels manufactured at testing time for the 85....
     
  9. tdiggity

    tdiggity Member

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    StepRob - It would be awesome if you guys switched wheels. For science!
     
  10. Designtime

    Designtime Member

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    LOL.
    I was thinking it would be nice for them to switch cars to see how the difference in weight affected consumption.
     
  11. Robert.Boston

    Robert.Boston Model S VIN P01536

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    Who was in front in the parade? Were you close enough that there could have been a drafting benefit to the follower?
     
  12. htsai14752

    htsai14752 Member

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    Great point! I was thinking the same thing. I also assume the extra weight between the wife and husband.
     
  13. StephRob

    StephRob Member

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    I was in the lead in the 60 kWh, but I really don't think drafting would have been an issue. He wasn't any closer than he would be in a normal situation driving through suburban streets. I should have had our 60 pound 7 year old along with me to even out the weight difference. We had fun and might try it again, so I'll bring the little guy along with me next time!
     

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