QUESTION: Heat Pump Efficiency—Just for S&G’s

[THEbuz]

Totally does not matter, but I often nerd out thinking about efficiency and optimization. (I was an efficiency expert for UPS for 15yrs.) As my title says, this one’s just for S&G’s…

Now that it’s warming up a bit outside, as I drove home today, the thought occurred to me to turn OFF the A/C and instead cool off by driving my 2023 Model Y (LR/AWD) with the window/s rolled down—ya know, to save energy. (Still thinking like an ICE driver—so help me.)

Then, a few thoughts occurred to me:
1) The heat pump should be much more efficient than the A/C system in an ICE vehicle.
2) Turning OFF the A/C in my Model Y and driving with the windows rolled down just might use more energy than the heat pump A/C system on account of the additional drag caused by having my windows rolled down.

Anyone care to weigh in on this? Thoughts…???

 

[BitJam]

There is a lot of info about this including a TMC thread:

Windows Down? or Air Conditioner? Whats more efficient?

Now that there are many people out there with Model 3's.....which situation do you find to be most efficient? Any non-theoretical real world data?

teslamotorsclub.com

The general consensus seems to be windows down is better at slower speeds (below 40 mph) and windows up with AC on is better at higher speeds (above 70 mph). But there is a lot of disagreement including a post in that thread that says windows down on their Model 3 is almost always better even on the highway.

The heat pump cools like a normal (perhaps very efficient) air conditioner. I'm surprised that windows down is better at 40 mph for an EV. Tesla nixed conventional door handles on the 3 and Y presumably to help with efficiency but I doubt aerodynamic handles (like the aftermarket ones I have) would add more drag than open windows.

Of course, my dog sticking his head out the window is not helping efficiency.

The rough 40/70 mph rule is for ICE vehicles. Since EVs rely more on aerodynamics and since their AC is probably someone more efficient than ICE AC I'd think the limits for EVs would be lower but I have not seen any hard evidence for this.