Roof box carrier range efficiency on R1T (installed Thule Atlantis 1800 XT Roof Box)

[Scottm]

I just wanted to share some data in case anyone else is interested. I'm planning on using my Thule Atlantis 1800 XT Roof Box rooftop carrier when we go camping later this summer on my R1T with 20" AT tires and I was wondering how much of an efficiency hit I would take by placing this on above the cab on the Rivian cross bars. So yesterday and today I did a test loop out of Eugene, Oregon up highway 58 with the carrier on and off. Highway 58 is a two lane highway without driver assist available so I set ACC at 67 mph to try and keep things consistent, but I was also at the mercy of other traffic so a fair amount of the time I was going 50-55mph with both scenarios. The weather also didn't cooperate with my test and yesterday was a fair amount warmer than today so probably more AC. I kept the same temp in the car on auto and ran in All Purpose auto ride height. For both runs I charged to 75% with 218 miles of predicted range. Here are the results:

With rooftop carrier:
Total distance: 65 miles
Average Speed: 47mph
Duration: 82 minutes
Weather: 82 degrees, 8mph wind out of NNW
Total energy: 31.4 kWh
Remaining range: 145 miles, 50%
Efficiency: 2.07 mi/kWh

Without rooftop carrier:
Total distance: 65 miles
Average Speed: 48mph
Duration: 81 minutes
Weather: 65 degrees, 8mph wind out of WNW
Total energy: 30.5 kWh
Remaining range: 147 miles, 51%
Efficiency: 2.14 mi/kWh

So this works out to about 3% lower efficiency with the carrier on which is better than I was guessing. And I think the AC ran more with the warmer temperatures yesterday with the carrier on, so the efficiency hit might even be less than this. There was definitely a lot more wind noise with the carrier on when I turned in to the wind, so I definitely won't have it on unless I really need the space.

Sponsored

 

[SSteveEV]

Thanks for the helpful test! I was annoyed my box is a hair too long to fit about the bed but 3% isn't too bad on the roof. How was the noise?
Enjoy your trip

 

[Scottm]

Thanks for the helpful test! I was annoyed my box is a hair too long to fit about the bed but 3% isn't too bad on the roof. How was the noise?
Enjoy your trip

I wish mine fit over the bed too, but this is not a bad alternative. When there was a headwind there was a fair amount of noise, didn’t notice too much with a tailwind. I just turned up the music and it wasn’t too bad.

 

[Rob O]

I did about 2500 miles with a Thule Motion XT XL “range robber” over the cab of my R1T: Bend, OR to San Diego area, around SoCal then back to Bend. A lot of interstate and highway miles, some local, tons of head and crosswinds, with too many variables to really assign efficiency hit to the box itself … but I’d estimate it’s more like 10%.

I think you’ll find, once you really get out and on the road, it’s worse than 3%. That stretch you tested on is a “better case” scenario, with speeds under 70 and a lot of regen opportunities. Get on the open interstate for a few hundred miles, where the electric motors are constantly pushing this brick with a box on top through the air, and you’ll see it dip.

Over the 3000 miles I drove (a few hundred with the box off) I saw 1.92 average. Again, lots of other variables and I was local for about 1000 of those miles (meaning more efficient driving scenarios, unloaded, box off, etc).

 

[Chewy734]

@Rob O where did you take that photo? Looks beautiful out there!

 

[Rob O]

@Rob O where did you take that photo? Looks beautiful out there!

North side of Mt Shasta. Can confirm … is beautiful! ?

 

[Gixxer]

I see these alot on different vehicles pretty sure it's hurts mileage at interstate speeds but probably not as much on lower speed roads. Interstate purpose wouldn't it be better if you find the I ones that fit on the trailer hitch (Aerodynamic). Easier loading and unloading thinking. Although this does look sleek in a way but not aerodynamic.

 

[Scottm]

I did about 2500 miles with a Thule Motion XT XL “range robber” over the cab of my R1T: Bend, OR to San Diego area, around SoCal then back to Bend. A lot of interstate and highway miles, some local, tons of head and crosswinds, with too many variables to really assign efficiency hit to the box itself … but I’d estimate it’s more like 10%.

I think you’ll find, once you really get out and on the road, it’s worse than 3%. That stretch you tested on is a “better case” scenario, with speeds under 70 and a lot of regen opportunities. Get on the open interstate for a few hundred miles, where the electric motors are constantly pushing this brick with a box on top through the air, and you’ll see it dip.

Over the 3000 miles I drove (a few hundred with the box off) I saw 1.92 average. Again, lots of other variables and I was local for about 1000 of those miles (meaning more efficient driving scenarios, unloaded, box off, etc).

Oh I’m sure the efficiency hit would be higher at interstate speeds, but this test is more representative of typical drives I would do around Oregon.

 

[Bar_Down]

Thanks for the validation! I wasn’t as scientific as you, but I estimated my Thule Motion XL size box only impacted my range on my R1S by less than 5%.

bonus tip: drafting an 18-wheeler really improves range.. by 10% or more.

 

[brancky3]

… And I think the AC ran more with the warmer temperatures yesterday with the carrier on, so the efficiency hit might even be less than this.

To be fair I think our trucks are going to be more efficient at 80 degrees ambient compared to 65, even with AC running. EVs do not benefit from cooler weather, that’s for sure.

 

[Rob O]

Oh I’m sure the efficiency hit would be higher at interstate speeds, but this test is more representative of typical drives I would do around Oregon.

That’s fair. I drove around Bend with mine on for a week or so prior to the road trip, and it didn’t appear to have any negative effect. Of course, that lulled me into thinking maybe it would be fine once I was in the highway too. ??

 

[Robin]

I did about 2500 miles with a Thule Motion XT XL “range robber” over the cab of my R1T: Bend, OR to San Diego area, around SoCal then back to Bend. A lot of interstate and highway miles, some local, tons of head and crosswinds, with too many variables to really assign efficiency hit to the box itself … but I’d estimate it’s more like 10%.

I think you’ll find, once you really get out and on the road, it’s worse than 3%. That stretch you tested on is a “better case” scenario, with speeds under 70 and a lot of regen opportunities. Get on the open interstate for a few hundred miles, where the electric motors are constantly pushing this brick with a box on top through the air, and you’ll see it dip.

Over the 3000 miles I drove (a few hundred with the box off) I saw 1.92 average. Again, lots of other variables and I was local for about 1000 of those miles (meaning more efficient driving scenarios, unloaded, box off, etc).

Awesome photo ?

 

[djsider2]

So it sounds like you were able to get the box onto the rivian cross bars. Sounds like good news as I have a pretty lightly used Thule Atlantis 1600 XT that I would like to continue using.

Sponsored