AC vs Windows down

AC vs Windows down

I know with ICEs it is less fuel efficient to have windows down
as show here:

However i was wondering if anyone has come across info with a fully electric car such as the model S or others.

edit: i realized that i wrote more fuel efficient by accident, changed to less

Silver2K | 17. elokuu 2016

I love opening all windows except the back passenger. it really does not hurt the power consumption much at all.

Captain_Zap | 17. elokuu 2016

We've come a long way, baby.
The event did stir up quite a debate as to whether rolling down the windows was worse than running the AC.

chasecorpus | 17. elokuu 2016

@silverp85plus Same here. My girlfriend hates it though, her hair gets all messy haha.

My concern is that an ICE(if i remember correctly) AC runs off of electricity which it gets from gears turning because of the ice engine. but in an all electric car I'm guessing its directly from the battery and didn't know if those logistics effect the energy usage differently

EVRider | 17. elokuu 2016

Do whichever is more comfortable. Whether one is better than the other depends on how cool you keep the car and the outside temperature. The AC uses less energy than the heater. | 17. elokuu 2016

Best efficiency is with Windows up, no AC! Ok, the jury is out on Windows vs. AC. Various articles on ICE cars seem to all agree below about 40 MPH open Windows is more efficient. Above that is more debatable, with some not finding any difference until 75 MPH (where AC starts to get better). Different vehicles act differently making it hard to generalize.

As for AC technology, on ICE cars, the compressor is driven directly from the motor via a belt. It generates more heat, so the radiator fan may need to be on longer as well. Most of these fans are driven electrically today as it is more efficient. On the Tesla, the compressor is electrically driven and I belive powered from the high-voltage battery (not the 12v battery). It also has electrically powered radiator fans that turn on as needed.

dansplans | 17. elokuu 2016

It should be simple enough to run various scenarios in an EV to test the idea fully. You can't get detailed enough information from an ICE vehicle licensed for road use.

Much has been made of drag coeffecients etc when discussing aspects of EV's. My gut feeling is that windows up would be the clear winner in most tests, with very low speed being the neutral or windows down victor.

chasecorpus | 17. elokuu 2016

I think whenever i get my model 3, i will definitely test this out.

my current car, an old ford Taurus doesn't have A/C as i replaced it with a pulley block because it was cheaper.
It will be nice to have A/C again haha.

DTsea | 17. elokuu 2016

clearly though the cabin is a lot noisier with the windows open, so I keep them closed.

Silver2K | 17. elokuu 2016

Clearly the open window idea is better on energy consumption!

A/C guys are clueless! PFFFFF as if!

carlk | 17. elokuu 2016

Probably even more so with an EV since air drag is by far the biggest factor in energy use at highway speed. AC actually uses very little energy. Heater is another story though.

Silver2K | 17. elokuu 2016

this carlk guy is nuts! open windows are better!


RedShift | 17. elokuu 2016

Just take off your clothes and drive without the AC on. No more debate!

carlk | 17. elokuu 2016


I'll open it when I need to throw you out of the car. ;)

Silver2K | 17. elokuu 2016

OK so red is against a/c

carlk is now pro window!

dansplans | 17. elokuu 2016

I would have thought there would be a lot of Mac users here.....

RedShift | 17. elokuu 2016

Look, we need to determine with max advantage with anew item: windows up and no AC vs windows down vs AC on and windows up.
To do the first item we need to take our clothes off. That's all I'm saying.

dansplans | 17. elokuu 2016

Anything that saves weight. A good opportunity to eject the old ball and chain too?

Silver2K | 17. elokuu 2016

no carl is pro mac, but pro window in the car.

everyone do what red said, i'm just supervising!

uh, keep skivvies on please and red's got it from here!

holidayday | 22. elokuu 2016

Windows vs. AC depends on temperature outside.
In a Tesla, you likely pre-condition the car before you get to it, so AC wins before you get to the car.
In an older car, you open the windows and let the AC blow just to get the inside temperature the same as outside (for example, it's about 130 degrees inside the car on a 95 degree day, keeping the windows closed makes the AC take much longer to cool the air. Just opening the windows will quickly moderate it back to under 100 degrees.)
If it's nice outside, having the breeze flow with the windows open is a way to get nice fresh air. Under 35 miles an hour, this will not really impact range. Above 35, and especially above 55, this significantly affects range due to the turbulence created by the open windows. AC is much better for fresh air above 35, and especially above 55 Miles an hour.

AC is so efficient that I use it almost exclusively for cooling the car after the initial windows down for quick car cooldown on the hot summer days - since I drive a non-Tesla.

ernie | 22. elokuu 2016

When running AC on a hot summer day, best to recirculate and to not select the option on dispursal which includes blowing air through the windshield defrost vents. Concentrate air on you. Makes a hugh difference in power usage. Plus there is full air filtration for those of us with alergies even on recirculate, just not the positive pressurization which is only really necessary when passing a skunk.

Haggy | 22. elokuu 2016

As for AC technology, on ICE cars, the compressor is driven directly from the motor via a belt.

If you want to get into almost irrelevant details, the flywheel will be free spinning when the AC is off, meaning that the minuscule drag on the ball bearings will be a factor, while when the AC is on, the solenoid will be powered, thus a minuscule amount of electricity will be needed to get the clutch to stay engaged, in addition to the drag on the belt from turning the compressor shaft. All that's for the ICE.

What does all this mean? It means that when you plug in at night and get up the next morning, your car will be charged. It will use so little electricity compared to running the car that you won't see the difference in your power bill compared to driving with the windows open, and there are so many other factors, such as how often you launch from a red light that will make a bigger difference. On a road trip, it won't mean additional stops at superchargers, or additional time charging that would amount to anything noticeable. If you stop to eat while you charge, you aren't likely to ever see a difference.

There are a lot of things that make a difference in theory, but are of little or no practical concern. Whether you keep an umbrella in your trunk makes a theoretical difference in efficiency, as does whether you go on a diet and weigh less. In theory if a supermodel jumps into the ocean, the water level of the entire ocean rises worldwide since her body displaces the water. In theory if I shout for a month straight, I'd generate enough energy to heat a cup of coffee. But in practical terms, the amount of time people spent contributing to this thread could have been spent giving a single speech on Wall Street that would have paid for the air conditioner use for all of us for the life of our cars. That's assuming any of us can get a high paying job giving speeches to Wall Street firms out to rig the US economy.

Silver2K | 22. elokuu 2016


look at what you started!

Ross1 | 23. elokuu 2016

Why not place a bet and the loser leaves the forum?

dansplans | 23. elokuu 2016

@Ross lmao

lilbean | 23. elokuu 2016

You're so funny, @Ross :)

Ross1 | 23. elokuu 2016

@dansplans: didnt you leave the forum? What happened?

Silver2K | 24. elokuu 2016

Windows down is best!!

(Exit stage left) | 24. elokuu 2016

Someone should do a study! Perhaps front Windows down 36% and rear Windows up 47% is ideal with A/C at 12% at 75 degrees outside? Just because there are an unlimited number of configurations of Windows and A/C settings and outside temperatures, Tesla should stop everything they are doing and figure this out! With a small team of 500 testers, I'm sure we can get the answers in 20 or 30 years :)

dansplans | 24. elokuu 2016 +10

lilbean | 24. elokuu 2016


Silver2K | 24. elokuu 2016

oooh.. can I be a tester for 30 years?

1st I will need an official company car supplied for next 30 years...... well, there is not second really, stick to the first request please.

thank you!