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Windows up, AC On vs. Windows down, AC off

Discussion in 'Model S: Driving Dynamics' started by ada43952, Jul 19, 2017.

  1. ada43952

    ada43952 Member

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    I seem to remember being told that in an ICE vehicle that it's actually more efficient when driving long distances (non-city driving) to drive with the windows up and AC on than windows down and AC off. I think the idea was that the additional drag caused by the open windows would out weigh the added fuel used by the AC.

    My question is, does this hold true for EVs, and Tesla's Model S specifically? With the low drag coefficient, is it better to have the AC on and windows up or AC off and windows down?
     
  2. scaesare

    scaesare Active Member

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    In my experience as you approach highway speeds the car is more efficient using A/C instead of windows...
     
  3. jdowell362

    jdowell362 Member

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    Yeah I mean no matter what the drag coefficient is, it gets destroyed on every windows are down. All that air coming in is the effect of the car pulling on the air around it while moving. It'll always be better to have the windows up beyond 50ish mph.
     
    • Like x 1
  4. supratachophobia

    supratachophobia Active Member

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    Mythbusters did this. Low speeds, windows. High speeds, AC.
     
  5. croman

    croman Active Member

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    AC in my car is far more efficient than heat. I can get well below 290wh/mi at 75mph on days <90F keeping temp at 73F and using AC. When I use windows my wh/mi is more like 315 and its very loud.
     
    • Informative x 1
  6. supratachophobia

    supratachophobia Active Member

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    I have also noticed that watts per mile with AC on being lower at faster speeds than with windows down at said faster speeds.
     
  7. kev1n

    kev1n Member

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    for me, windows up/ac on all the time. i dont even open the windows anymore since its so loud outside lol
     
  8. TSLA_maybe

    TSLA_maybe Member

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    I see much better wh/m (>30) with windows up/AC on (67F) than windows down/AC off for both in-town and highway driving. Even better when highway driving when cruising at constant 70mph, I've had wh/m of ~270
     
  9. Naonak

    Naonak Member

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    I've tested it. Same stretch of highway, same day/temp/speed/etc... AC is more efficient than windows down by quite a bit (about 70 WH/mile). I didn't test low speed driving though. This was at ~75mph for 14 miles.
     
    • Like x 1
  10. tstafford

    tstafford Supporting Member

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    Regardless of WH/mile, I'm rolling with the AC. It's hot as Hades in Nashville.
     
  11. clostridium

    clostridium Member

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    There's no doubt that the AC is more efficient than windows down. The AC doesn't really have a big impact on range to start with - try the calculator on the Tesla website to see how the AC impacts range and it's not a huge amount. My experience on my vehicle is that it's even less than their calculator.
     
  12. doctorwho

    doctorwho Member

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    With a name like Clostridium I'm surprised that you have any need for oxygen:p
     
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  13. Tangible

    Tangible Member

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    i don't think ICE cars are any different from EVs in this regard. Modern aerodynamics are ruined by open windows. It would be nice if cars came with efficient fresh air intakes, emitting outside air through the AC vents, but this doesn't seem to be available on current vehicles.
     

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