MY vs MS air conditioning?

[JayInJapan]

Hello all:

I’m coming from driving a 2014 MS. I used to be comfortable on hot, humid days with the air con on recirculation at 26 C degrees. Now, in my 2023 MY, I need to set it at 23.5 or 24 to feel comfortable. I see a huge increase in battery use at these levels compared to when I try to get by at 26. Is it common to need the setting so low or should I have it checked out?

 

[exxxviii]

I live in a region with very high humidity and summer temperatures 32° C or higher. I have always set my car automatic HVAC temperatures around 22° C, depending on the car. I have my Tesla Model Y set to 21.5°. My old car's similar level of comfort was 22°. (I think I would die if my car setting was 26°, and I don't think I would survive at 23.5°.)

 

[Konicom04]

model Y and 3 only turn on occupied seat vents by default, which in my experience makes the AC super noisy and slow to cool cabin / maintain comfort level.
I always click on passenger's side vent to activate it, and if its really hot, also turn on rear vents

 

[TomB985]

Hello all:

I’m coming from driving a 2014 MS. I used to be comfortable on hot, humid days with the air con on recirculation at 26 C degrees. Now, in my 2023 MY, I need to set it at 23.5 or 24 to feel comfortable. I see a huge increase in battery use at these levels compared to when I try to get by at 26. Is it common to need the setting so low or should I have it checked out?

I think you’re overthinking it, to be honest.

These HVAC systems are similar to every other climate control system. It commands the system to provide sufficient cool air to get to a certain set point. I suppose it’s possible there are differences in cabin temperature probe location or calibration between this and your previous car, which means you have to set a lower temp to get to the same comfortable spot where you’re sitting.

If there were a problem with the system, it would run harder to reach that same set point, but it wouldn’t be noticeable to the driver unless it could no longer keep up. The fact that you’re comfortable at a 24º set point means the system is accomplishing what you’re asking it to do. I’ve never found A/C use to make much of a difference in my energy consumption.

 

[Darmie]

I'm not saying the difference is freon, but maybe they changed the type freon between those years.

Here’s what you need to know about R-1234yf

www.bgprod.com

 

[TomB985]

I'm not saying the difference is freon, but maybe they changed the type freon between those years.

Here’s what you need to know about R-1234yf

www.bgprod.com

They probably did. Has nothing to do with the OP’s concern, though. R1234yf is relatively new, and very expensive compared to the previous R134.

 

[TomB985]

I decided to indulge my nerdery and pull up the service manual. It looks like earlier Model S used R134a. Both specs are showing.

 

[danp]

One thing that helps significantly is getting the windows tinted with high quality heat rejecting tint. First thing I do on every car I buy.

 

[TomB985]

One thing that helps significantly is getting the windows tinted with high quality heat rejecting tint. First thing I do on every car I buy.

That’s a good point. A good friend of mine in Texas just bought a new Model Y. He sent me this in a text message about an hour ago:

Fun experiment with the ceramic tint vs Texas 103 degree direct sun heat. It went 70 degrees to 100 degrees in 15 minutes yesterday. Today 30 minutes ish. It slows the thermal impact but like any space, time adds up.

Another test will be the battery impact on a road trip. According to the Tesla tips, AC caused a 2.4% impact to the battery on the trip.

I told him that I don’t think he’ll see much efficiency improvement because of how little HVAC consumes. <1 kW draw from the compressor is almost nothing against the 30-60 kW the motors will pull going down the road.

 

[danp]

I told him that I don’t think he’ll see much efficiency improvement because of how little HVAC consumes. <1 kW draw from the compressor is almost nothing against the 30-60 kW the motors will pull going down the road.

Yup, AC doesn't consume much, unlike heating (even with the heat pump).

 

[danp]

Also, OP, not sure if that profile photo is accurate but if you're going from a metal roof to glass, it's going to make a different in terms of cabin heat, regardless of the UV protection Tesla claims it has. Roof sun shade will help along with a good window tint.

 

[Darmie]

They probably did. Has nothing to do with the OP’s concern, though. R1234yf is relatively new, and very expensive compared to the previous R134.

I was thinking the new Freon is not as efficient as the older as R12 was more efficient than 134.

 

[TomB985]

I was thinking the new Freon is not as efficient as the older as R12 was more efficient than 134.

Maybe, but the system operates the same. It commands lots of cool air until it hits the set point and then enough cool air to hold it.

If the system had to work harder to get to that point, it would t matter to the driver because it still gets there. “There” being the same 24° or 26° point the driver commands. You could have a giant Lennox commercial unit on the roof and 24° is still 24° at the same measured location.

 

[JayInJapan]

I think you’re overthinking it, to be honest.

These HVAC systems are similar to every other climate control system. It commands the system to provide sufficient cool air to get to a certain set point. I suppose it’s possible there are differences in cabin temperature probe location or calibration between this and your previous car, which means you have to set a lower temp to get to the same comfortable spot where you’re sitting.

If there were a problem with the system, it would run harder to reach that same set point, but it wouldn’t be noticeable to the driver unless it could no longer keep up. The fact that you’re comfortable at a 24º set point means the system is accomplishing what you’re asking it to do. I’ve never found A/C use to make much of a difference in my energy consumption.

The difference in consumption is huge between the 2 temps I noted. 26 gets me 155kWh/km; 24 is 175kWh/km. “Overthinking” is a rude exaggeration; thinking and observing are what I’m doing.

 

[JayInJapan]

One thing that helps significantly is getting the windows tinted with high quality heat rejecting tint. First thing I do on every car I buy.

Tinting done on Day 1, although I didn’t touch that glass above my head. I miss my solid roof.

 

[JayInJapan]

Also, OP, not sure if that profile photo is accurate but if you're going from a metal roof to glass, it's going to make a different in terms of cabin heat, regardless of the UV protection Tesla claims it has. Roof sun shade will help along with a good window tint.

You recommend tinting the roof?

 

[JayInJapan]

I’ll add here, thanks to all who responded. I’ll take a drive today and test a couple of things out.

 

[CaseyL]

model Y and 3 only turn on occupied seat vents by default, which in my experience makes the AC super noisy and slow to cool cabin / maintain comfort level.
I always click on passenger's side vent to activate it, and if its really hot, also turn on rear vents

I do this as well. I wish this was the default setting.

It's hard to cool the whole car with just the driver's vent.

 

[Konicom04]

I do this as well. I wish this was the default setting.

It's hard to cool the whole car with just the driver's vent.

Yes!,
As in my old Volts - there should be a ECO and COMFORT setting, ECO to just "lick" the energy at minimum, COMFORT to go nuts and provide comfort

 

[GData]

Yup, AC doesn't consume much, unlike heating (even with the heat pump).

Heating by X degrees uses more energy than cooling by X degrees?

If that's true then people in mild climates shouldn't tint their windows because it'd make the cabin colder in winter which would more than offset the energy savings in summer