How much does running the AC reduce range in a Rivian?

[Rivianready]

I was reading the following article about the Hyundai Ionic 5 and how much running the AC significantly reduces its range. How much does running the AC reduce range on a Rivian R1T or R1S with a large battery pack? (I have an R1S in order.) Thanks!

https://www.motortrend.com/reviews/...-review-update-5-air-conditioning-hot-weather

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[Donald Stanfield]

In my experience little to no difference while driving. Once it cools down it doesn't take a ton to maintain. If you are preconditioning all the time maybe but just driving with the ac on is no big deal. The heater however has a pretty significant impact.

 

[Cactus]

I did an experiment with my R1S last week.
Background:
Many on this forum have noticed a dramatic drop in efficiency (mi/kwh) when getting in a hot or warm R1S and running the AC while it does its "full throttle weed wacker" impression to make the cabin cool, often unsuccessfully. My R1S goes from a normal 2.2+ mi/kwhr to <1.7 mi/kwh. I have posted this efficiency in another thread.

Methods:
I decided NOT to turn on the AC during my drive home from work (initial cabin temp >125°F) and simply drive ~12 miles with vents blowing and windows cracked about 2 inches WITHOUT the AC on. Then take a picture of the energy graph when arriving home.

Results:
Besides being pretty sweaty by the time I got home, I noticed that the mi/kwh graph does essentially the same thing as when the AC is ON during the same drive home. See pics below. Efficiency takes a big hit for the first ~5 miles, then gradually gets better.

Discussion:
This leads me to suspect that the vehicle might be trying to cool the battery pack, and that the AC compressor (despite all the racket) doesn't use a lot of power.
Anyone else notice this, or want to do a similar experiment? What do folks think about this idea?

 

[Rivianready]

Interesting info. Thanks. Someone above mentioned heating and that it takes more energy. What’s your experience with that?

 

[cbrcanuck]

Purely anecdotal, but I find if I’m actually driving (ie traveling significant miles in one trip) it doesn’t make a significant enough difference to really care much, but if I’m in and out of the truck and it’s starting and stopping or I leave it on so that it auto turns on/off with proximity, it makes a much bigger dent in efficiency/mileage.

Most of my driving is in/out with short trips around the city and If I’m trying to be efficient, I’ll make sure to leave it off when I’m done driving and just turn it back on when I need it, generally venting with windows to cool it down first.

Winter will be a new experience!

 

[Lizardo]

Not willing to find out this summer … too hot

 

[Redmond Chad]

TL/DR: It's complicated. But in general, cabin AC isn't a huge hit, at least not if you're doing a long freeway drive where you are most likely to be concerned about range. Heat in winter is a larger concern.

OCD:

I haven't done any measurements in my Rivian, but I have done some in past EVs. Some general principles:

AC uses energy, measured in kWh. Range is measured in miles. Range with AC depends on mi/kWh, which is efficiency. So how much AC affects range depends on how much energy the AC is taking (which varies by ambient temps and your settings), and your current efficiency (which depends on many factors, but the big one is speed).

This means that to answer the question of how much AC affects range, you need to know at least the following: what's your current efficiency, how fast are you going, how far are you going, what are ambient temps, what is AC set at. (Plus more like solar gain, how warm the components were to start, etc - as cbrcanuck notes, these can be very significant. Start-up costs are much greater than maintenance costs. But we will ignore them here as I assume a question about range is more about a long continuous drive on the freeway, rather than multiple small trips around town. My answer would be different if the question was about efficiency).

With no HVAC going, traveling slower generally improves your efficiency (well, there's a lower bound probably somewhere around 25mph; but it's going to take many hours of driving at that speed to get where range is a concern). However, HVAC pulls energy as a function of time. So the slower you are going, the larger the HVAC's relative hit will be (because you are traveling fewer miles per kWh consumed for AC).

From another EV, here's a graph where the top line is rated range without HVAC, and the shaded area below it is what your range might be depending on how much HVAC you are using. Note that the effect is MUCH larger at lower speeds.

Also note this was calculated for resistive heat in a small vehicle, rather than for AC via heat pump in a large vehicle. So these numbers are definitely NOT applicable to the Rivian, but the general concept of how AC (w.r.t. speed) affects range is.

Cactus' experiment illustrates something important that I have glossed over so far: I keep talking about HVAC as if it's just a setting for the cabin. But in my previous measurements, I have found that about 2/3 of the heating/cooling energy is for the battery pack, rather than the cabin. With the Rivian's large and thick pack, this might (?) be an even larger factor - sometimes, as there's plenty of variables here too.

As for AC versus heat: AC is via heat pump; heat in current Rivians is resistive. So heat is less efficient and takes more energy. Add that to the fact that batteries typically like things warmer than people do, and you generally end up with a lot more range hit in winter due to heat than in summer due to AC (at least in places with seasons).

 

[evhelphub]

I live in Texas where it's hotter than the sun. Reduction is very small on full blast. Less than 10%. Probably closer to 5%.

I like to mention to others that the insulation in the R1s is fantastic so you don't need to run it full blast for very long to keep it cool.

My ID4 on the other hand does not have any insulation at all and it definitely cuts 15% or so of the range. It has a cover for the glass roof but as soon as you turn the fans down the heat comes back instantly. Not so in the Rivian.

 

[Cactus]

Cactus' experiment illustrates something important that I have glossed over so far: I keep talking about HVAC as if it's just a setting for the cabin. But in my previous measurements, I have found that about 2/3 of the heating/cooling energy is for the battery pack, rather than the cabin. With the Rivian's large and thick pack, this might (?) be an even larger factor - sometimes, as there's plenty of variables here too.

That's what my experiment would suggest– All other variables are very similar (same ambient temp, same route to and from work, same times of day)– if the efficiency graph looks nearly the same with AC on vs AC off, I bet the first several minutes when ambient temps are high are to cool/condition the battery which seems to be a big hit to efficiency until the battery temps become nominal. Can anyone with a connection to Rivian engineers verify? What is the optimal/pre-set battery operating temp in a Rivian?

 

[LL75]

This is my 190 miles trip. It used 3kwh for cabin and battery with 2 and 3 ac fan speed in this 105 degree weather

 

[JoulesVerne]

The original article was kinda crap anyway. The writer had it on full blast at the coldest setting.

 

[SRO]

If I had the option I would not get the sky roof. When I got my T last August I thought the AC was terrible. This spring I installed a sun shade and this summer the AC works a whole lot better. I was surprised about the difference. Maybe OTAs are a factor?

The only ones that can see the glass roof are those in the back seat. I’ve only had people back there twice. My grand daughters thought it was cool.

 

[Rivianready]

If I had the option I would not get the sky roof. When I got my T last August I thought the AC was terrible. This spring I installed a sun shade and this summer the AC works a whole lot better. I was surprised about the difference. Maybe OTAs are a factor?

The only ones that can see the glass roof are those in the back seat. I’ve only had people back there twice. My grand daughters thought it was cool.
[/QUOTE

I agree. The sky roof desperately needs an automatic cover. For a car this expensive, it’s unforgivable that they don’t offer one. When I

 

[SolartoEV]

This is my 190 miles trip. It used 3kwh for cabin and battery with 2 and 3 ac fan speed in this 105 degree weather

I think that is just for the charge session. Not a trip meter correct?

 

[LL75]

I think that is just for the charge session. Not a trip meter correct?

I charged my r1s back to the original percentage I started with

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