Model 3 Roof Rack Consumption Test

Last week we received and installed the new Tesla Model 3 Roof Rack on our car – go check out the install if you are curious.  One of the comments I have been receiving and seeing online in the forums is “how does the roof rack affect your efficiency?”  I decided to do a controlled test to find out!

I created a test plan to help ensure I had control over as many elements as I could during the testing.  Since I already had the roof rack and Yakima ski box installed, Test #1 started there!  Check out the video below to see how we conducted the test, and my random thoughts that popped up during the testing process.

Now that you’ve watched the video or read the test plan, you understand how we controlled the test.  The results are tabulated below – bear in mind that I have winter tires on and it is cold outside, so the bare roof consumption is likely higher than what you were probably expecting… but that doesn’t matter, as what I was interested in finding out is how the consumption is increased by adding the rack, then the ski box.

Table 1

Looking at the consumption table for the downhill and uphill only segments – you’ll see that the difference in consumption is essentially the same as the overall difference in consumption presented in the second table.  So I think I was successful at removing the element of differences in elevation from the equation.  The only thing I didn’t control for that might have had some effect on the testing is whether that battery has different internal resistance at different states of charge – I don’t think it does, but if you happen to know, chime in with a comment below!

Table 2

So given the approximate error in the measurement/calculations, it appears that the difference of installing the rack is negligible – a few % at worst.  Adding the ski box however, that increased consumption on the order of 10 – 15%.  I’m going to use 15% in my future trip planning when I use A Better Route Planner.

But now for some context!  Sure I’m increasing the consumption on my Model 3 when I install the roof rack plus ski box, but what is my alternative?  Well in my case, I came from a Subaru Forester, and while it has more cargo room than the Model 3, it still doesn’t fit skis inside the car any better than the Model 3 (actually it is worse, as the Model 3 has a longer “load floor”, so fits our XC skis better), so I had the ski box installed on that car anyways!  So let’s compare consumption for the Subaru vs the Model 3:

I think the overall net benefit here is pretty clear!  Five times more energy to move a similar sized vehicle, similar weight vehicle, with the same number of occupants and their ski gear… the Model 3 clearly wins here, even with the roof rack installed!  The amount of extra energy needed to move the Forester is just atrocious.  Even compared against a Prius (arguably the mainstream pinnacle of ICE efficiency), which at best has an average consumption of about 1/2 of the Subaru would still yield the Model 3 being 2.5x more efficient than the Prius!

If this content has swayed you to buy a Tesla, please consider using my store referral link to order:  https://ts.la/andrew71174, or give the code “andrew71174” to your Sales Advisor during your purchase.  Generally you will get some kind of benefit.

kootenay andrew

kootenay andrew

Andrew is an environmental engineer by day, "kid activity/school volunteer" by evening, and EV advocate / blogger in his remaining spare time.

He is very passionate about the future of energy generation & usage.He prefers bikes to cars, but acknowledges that Canadian cities have been developed primarily with cars in mind, so if we're going to drive, let's make them all EVs!(But let's get EV buses and take those where possible first.)
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kootenay andrew

Andrew is an environmental engineer by day, "kid activity/school volunteer" by evening, and EV advocate / blogger in his remaining spare time. He is very passionate about the future of energy generation & usage. He prefers bikes to cars, but acknowledges that Canadian cities have been developed primarily with cars in mind, so if we're going to drive, let's make them all EVs! (But let's get EV buses and take those where possible first.)

8 thoughts on “Model 3 Roof Rack Consumption Test”

  1. Nicely done on the tests! These will be useful for my decisions for sure! I wonder what the difference in range loss would be when attaching a hitch mounted cargo box instead of a roof box. May be a bit less of a range hit?

    1. I imagine it would be less since the air speed is lower in that region. However I don’t have a cargo box so can’t test it yet. Maybe I can find someone to lend me one in the late spring, once I have my receiver installed. I will be doing a similar test with my hitch mounted bike rack.

  2. https://youtu.be/NSp0DQ_Q_hU

    Link to my video on the impact of roof racks on aerodynamics. In this instance it moved the CD of the Tesla from 0.23 to 0.28 making it as bad as a Nissan Leaf. Comparisons to Subaru Forrester are just not Germain to this project and have no bearing on the negative aerodynamic effects of carrying loads on the roof of any car. A environmental specialist would know this.

    1. Hi John, I watched the whole video – good explanation of Cd and it’s relationship to range. We will have to respect each other’s opinion with regards to the roof rack + cargo box vs bare roof. If I had not been able to mount a box, I would not have bought a 3 – simple as that. The point of comparing to the Subaru is to show the huge net benefit by switching to a 3.

      Anyways, I have three other thoughts:
      – if one accepts that some people do in fact need a roof box (at least sometimes), then perhaps someone should put some effort into designing one with better aerodynamics – perhaps a better profile on the rear of the box, a focus on less protruding lips, etc. I did see an interesting feature on a Yakima box recently with what they call “Carbonite” texture – it has the small dimples on most of the box that one would find on a golf ball! I’m curious to see what difference that makes.
      – the bit about the trailer at the end really caught my eye; to go car camping with two kids and even our backpacking gear will be very challenging in the Model 3, so I have been wondering about renting a trailer when needed. I’ve looked around quite a bit, and have found a few trailers that may not be too bad (though they do not have the taper you spoke of) – an example https://eco-trailers.com/cub-caddy-trailers.php?fbclid=IwAR2EhKjjDPEIjMeEfXzhjCOE_hSex58yL-sNmsvqsxvvzyJbDskTJbSpmQA
      – lastly, when on road trips where the range between charges really counts, I will do what I did in my Leaf when using the heat in the winter; I’ll just slow down by 5 – 10 km/h, which will overcome most of the decrease in efficiency.

      Regards.

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