Model 3

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How does Tesla's 2021 heat-pump HVAC works?

Hey gang, new to Tesla here. Just like with most vehicles, auto HVAC never works for me, so I always operate it in manual mode. But with Tesla, I'd like to know what it's doing as far as energy consumption. For instance, I never turn A/C on in winter unless defogging is needed. But with no engine, if you turn A/C off and set temp to 70, and it's 50 outside, does the system still produce heat? What's the difference between using HVAC with A/C on and off, if the heat-pump has to work anyway? So what's the most efficient way to operate HVAC on this car for minimal energy consumption at the same set temperature? Always leave it in auto mode (where A/C turns light blue all the time)? And can you change fan speed and vent selection while still in 'auto' mode, like in some cars? On others, as soon as you change anything manually, auto turns off. I can play with that, but still want to know how to operate it in the most energy efficient way. Thanks.


  • No hvac expert here but I always thought using the ac in cold weather still runs the compressor a little to take the humidity out of the air. I think running in auto mode will turn the ac on and off as needed (as well as recirculate/fresh) to be most energy efficient. Not sure why automatic hvac doesn’t work for some people. Is it just that your comfort needs are so moody, that auto restricts your ability to tweak things fast enough?

    I sometimes turn off auto when I want cooler air in my face, so I get it sometimes. But most of the time auto works very well for me.
  • These 3 videos do a pretty good job of explaining how it works in great detail; although, it's referring to the Model Y I'm assuming it also applies to the Model 3 heat pump system.
  • I saw those, but it was only a general explanation of the system. No explanation on what the system is doing in auto vs manual mode in winter, for instance, like using just the fan, vs auto, with temp set to 70 while 50 outside. I could hear the system making more noise in auto, so I assume it's turning the A/C compressor on.

    My specific question is if you can get more heat in the cabin with just the fan engaged, and what the system is doing. I got the impression from those videos that ANY HVAC mode (even just the fan) runs the compressor, but that's not the case, so a little confused about that specific operation.
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