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A/C and Mileage

Discussion in 'Model 3: Battery & Charging' started by mrswayze, Jul 30, 2019.

  1. mrswayze

    mrswayze Member

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    I had a nervous experience today so I'm looking for information on how to factor in use of the air conditioning. Today I started on a 60 mile round trip via highway and farm roads in the 90 degree heat. A/C was set on 9 at 68 degrees. Starting out I had a 90 mile charge. When I got home it was down to 8. To conserve energy I turned off the A/C on my way home. Question: How much energy does air conditioning consume? Took delivery of my Model 3, btw, less than two months ago.
     
  2. Uncle Paul

    Uncle Paul Well-Known Member

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    A/C is not a big user of electricity. Heater is the bigger user.

    Range is calculated for you to drive relatively sedately. Imaging that if you were driving enthusiastically, that may have been a bigger factor in your reduced range.

    If you started out with a 90 mile range, drove 60 miles and had a remaining 8 miles (68 miles total) that is not much out of line. To get your estimated range you will need to drive under 60 mph, use your regeneration effectively, and drive smoothly along those farm roads.

    If you had some headwinds, rain or elevation changes, that also could explain your range evaporation.
     
  3. StealthP3D

    StealthP3D Well-Known Member

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    I have found the effect of A/C usage on the range to be insignificant or barely detectable. Opening your windows would affect range a LOT more.
     
  4. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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    #4 AlanSubie4Life, Jul 30, 2019
    Last edited: Jul 30, 2019
    What type of Model 3 do you have?

    I disagree with the above two responses. A/C is a lot less energy intensive than heat, for sure, I agree with that. But it is not “insignificant.”

    When it is blasting on a hot day, it may well be consuming 1kW of power (this is a ballpark number, not precise - and it varies a lot depending on how hard the AC is working). It may be even higher initially as it runs open loop to cool the car. You can measure all of this indirectly by plugging in the car with no charging taking place and measuring power consumption (and correcting for charger inefficiency).

    For an average trip speed of 50mph, that will add 20Wh/mi to your consumption. For an average speed of 25mph, that could be 40Wh/mi. (Watts / avg speed)

    I ask about your car type to assess the reasons your rated miles went down by 82 miles on a trip of 60 miles. Also would be good to know what was your average speed.

    In San Diego, it was hot this weekend, and
    I definitely noticed the effect of the AC use!
     
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  5. mrswayze

    mrswayze Member

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  6. ewoodrick

    ewoodrick Well-Known Member

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    Were you going 80mph+

    I find the AC works much better on auto.
     
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  7. NickFie

    NickFie Member

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    We took our Model S100D to some shore towns about 120 miles away. Cabin temperature set at 70 degrees, climate on Auto.

    Air temperature got near 100, strong sun, few clouds. We made a lot of short trips while we were there. Air conditioning sucked a lot of power.

    On the short hops, we used as much as 500 Wh/mile, down to about 300.

    290 Wh/mile on the ride home, after dark with cooler temperatures but higher speed.
     
  8. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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    Ironically, the faster you go the less impact AC will have.
     
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  9. ewoodrick

    ewoodrick Well-Known Member

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    But the faster you go, the worse the consumption. No, it's not the A/C, its wind resistance.
     
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  10. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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    That is correct. But what I said does not contradict that!

    However, AC use does increase the optimal speed for optimal range, slightly.
     
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  11. seattlite2004

    seattlite2004 Active Member

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    Yeah..not the same model...but it's a datapoint:

     
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  12. hoang51

    hoang51 Member

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    For me in the Performance trim, I would double the amount of range miles to compensate for AC or heat usage while driving. For example, a normal 4 miles round trip I usually drive consumes 4 miles of range with no AC or heat. But if I turn on the AC or heat while driving the same route, I'm expecting to consume about 8 miles of range. Works accurate enough for me to predict how much range I need for trips.
     
  13. darth_vad3r

    darth_vad3r Well-Known Sith

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    Why did you start the trip at 90, was it unexpected? Do you not charge up nightly to 50-90% as recommended?

    A/C ballpark is 1kW, if you use auto it’s more efficient and will adjust fan to hit your temp.

    If you averaged 60 mph, then over 1hr of driving, AC at 1 kW would consume 1 kWh of energy, or about 4-5 “miles” on your dashboard (for a car with 200-250 Wh/mi efficiency). Over your 60 mile trip, 1 kWh is 16.67 Wh/mi.

    If it’s hot and you are cutting it close, slow down by 10mph before shutting the AC off.

    Check ABRP’s charts, it seems slowing to 50 from 60 would increase your range by over 10%. The <17 Wh/mi A/C number above is <<10% of your consumption unless you are Uber-hypermiling at 170 Wh/mi ...
    [​IMG]

    source: Model 3 Consumption and Charging
     
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  14. darth_vad3r

    darth_vad3r Well-Known Sith

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    That might work well for short 4mi trips but throw that out the window for long trips. Heat can use 6x as much power as A/C.
     
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  15. Magnets!

    Magnets! Member

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    recirculate mode will save some energy once the interior has cooled below the external air temp. I also find that high fan speed is not always best for lkeeping the car cool. Yes, on startup to initially cool the car, but after that, lower the fan speed and the air will blow cooler.
     
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  16. darth_vad3r

    darth_vad3r Well-Known Sith

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    Summary screen cap:

    D9ED4491-6A63-4348-ABEA-E2CD0816D854.jpeg

    So ya, AC off he went from 340 -16 to 324 Wh/mi
    Slowing down 30% dropped him to 259 Wh/mi. Speed a much bigger factor.
     
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  17. darth_vad3r

    darth_vad3r Well-Known Sith

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    “auto” does all this for you automatically, deciding when to keep recirculate on based on exterior temperature (most of the time if it’s hot :)) and starting with high fan speed then lowering automatically once the set temp is reached (and raising again later if necessary).
     
  18. Rocky_H

    Rocky_H Well-Known Member

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    Over the past several years when I've had people who really didn't know anything about electric cars ask me questions, they did frequently ask, "How much does the air conditioning affect your range?" The first thing was to surprise them by pointing out that heating has a much bigger impact than A/C does. They are in the gas car mindset, where a gasoline engine is busy desperately trying to get rid of tons of heat energy out the radiator and tailpipe so it doesn't melt itself down. So heating the inside cabin of a gas car is always "free". An electric motor is so efficient that it doesn't have all that excess heat, so it has to run an electric heater to warm you up, and that pulls from the same battery as the "miles".

    And specifically, the reason why there is such an energy consumption difference is that air conditioning is a mechanical heat pump, which is way more efficient energy conversion than a resistive heating element.

    So I describe an analogy of a ranking of what items draw relative amounts of energy, descending order, but with different spacing of how much their impact is:
    (1) Moving the car. Adjusting your speed makes huge differences, even by 3 or 4 mph over longer distances.
    ...
    ...
    ...
    (4) Heat. Can be very noticeable in winters, and need to plan for it.
    ...
    ...
    ...
    (22) Air conditioning. Much less than heating, but still a little noticeable--maybe 5-10% difference in range.
    ...
    ...
    ...
    (1,556) Everything else. All other things are completely unnoticeable energy draws. I've seen people talk about headlights or wipers or the stereo or the touch screen consuming energy or shutting them off to extend range, which is total nonsense. They are so small compared to driving speed or HVAC that you would never possibly be able to detect any difference from those.
     
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  19. KenC

    KenC Active Member

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    So, AC has roughly a 5% hit on efficiency.
     
  20. Runebane

    Runebane Member

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    I think that hit may be more for a LR RWD as we usually are much lower wh/mi to begin with. Assuming it's a relatively steady 16 wh/mi to run the AC that is.
     

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