Here’s How Much A Roof Box Impacts EV Efficiency

Zach is back with his Hyundai IONIQ 5 where he puts on a roof box to see how much impact it makes to the range of his electric car.
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[@klossfam]

Zach kind of blows off the differences at the end. 3.2 with no roof rack vs 2.6 with rails vs 2.3 with box is HUGE. Owning 3 I5s in the family, 70 mph with nothing will be about 3.0 real world but vs 2.3 is not good. I can get 2.2 in my Lightning at 70. Essentially, your range is reduced by 25% or more. My advice: Take less crap on your road trips.

[@jamespaul2587]

Agreed, rails alone dropped efficiency by around 20% and the box another 10% however the lack of controlled conditions makes the comparisons less reliable. Some families need room for gear on road trips and camping, so he may not have a good option, other than a small trailer which may impact range more

[@0hypnotoad0]

I bring a roof box selectively on road trips. If I'm only driving and sightseeing I take off the rack and box and gain the range. If I'm going kayaking and camping I take the roof box and just drive slower and/or use backroads. A rear cargo carrier is a better option if you need extra cargo space on a long trip, it has a much more negligible impact.

[@philorgneopolotin8762]

Agreed. He really blew off the differences when 3.2 mi/kWh vs. 2.3 mi/kWh with the box means you literally get _40% more range_ with no box or roof racks. That’s massive. That could be the difference between getting like 210-215 miles on a road trip and _300_ miles the same scenario without the box. That honestly doesn’t sound as insignificant as he made it seem…

[@clasqm]

Bjorn Nyland had a video about two years ago in which he stated that you actually get better aero if you mount the box with the blunt end in front.

[@wojciechmuras553]

The one and only time I've ever been stranded in an EV was when I took a 30 kWh Leaf on a 100 mile stretch with no chargers. Usually, doing all the eco-driving possible, I'd arrive with a few % to spare, no big deal. But this time I had to take a roofbox, and underestimated the impact it would have... Was stuck for almost 4 hours, trickle charging from an outlet at a random gas station! However, maybe something good came of it, because next year that station had a 50 kW charger put in :)

[@mundoracer]

Seems like quite a bit of difference! Zach kind of down played it

[@HytelGrp]

Hi Zach, Time for Part 3, where you mount the box on the opposite way to see if it makes the vehicle appear closer to a teardrop shape and improves the efficiency.

[@crowfoot1199]

Yes please! I heard putting it on backwards helps with the efficiency a lot.

[@alejandrovieira6451]

I have the same box, and you likely would not be able to open the rear hatch if mounted backwards.

[@omelvold]

That’s true. Wouldn’t recommend it for other than testing purposes though. For safety reasons, and for optimal performance, you need a roof box specifically designed for backwards mounting. Check out Calix Aero Loader from Sweden.

@@omelvold Yes. Flipping most boxes backwards is more efficient, but way less stable.

[@fpartidafpartida]

So the bars are a bigger drainer than the box? Interesting.

[@Air-ic279]

Best efficiency is a rearbox on your future tow hitch. Almost no extra drag. For your Ionic 5 I would prefer the rearbox over a roof box.

[@justinfowler2857]

Doesn't the Ioniq 5 have rear vents that channel air to the back of the car? I wonder how a cargo box would affect said efficiency.

[@Bubbz2024]

I agree. I use the receiver hitch basket and bungee down a large plastic tote bin to my ID4. It's not as sexy as the Thule but easy to access and quick to take on and off

[@tubelator]

How is 2.3 vs 2.6 not a big difference ? Even 3.2 without is a hugeee diff

[@joniboulware1436]

@@Bubbz2024 Thule much more theft proof.

[@Bubbz2024]

@@joniboulware1436 how so? Thule is definitely less cumbersome but I have a hitch pin lock. Equally as secure as the Thule in that regard.

[@OverwatchPlaysGames147]

If you flip the box around backwards, it actually uses quite a bit less battery. The thinner edge toward the back allows for the air to detach a lot more cleanly without creating as much of dead zone

And you make your care less stable in the process.

[@wolfgangpreier9160]

@ Yes, please don‘t! The wing shaped design helps the car and creates downward pressure. If you flip the box around it acts as a wing and the car could fly. You do NOT want your car to fly! You are NOT licensed to fly your car!

[@robertkirchner7981]

It would be nice if someone made a cargo box that was designed to BE aerodynamic, instead of just LOOKING aerodynamic. A 28% hit in efficiency is nothing to sneeze at.

[@Matt-dx3wo]

ok so in your mind the bars hurt efficiency more than the box? doesn't add up, the 3.2 was on a different day.

[@Floridos]

The Moby Dick Box 2000 is far nicer. It is made of Polyester for more stiffness and tested for 124 mph (200 kmh) driving. This is normally meant for people who drive over the autobahn for their holiday trip.

[@timgurr1876]

Good to see some real-life testing. Maybe some video on your trip to Texas would be interesting regarding overall efficiency and number of recharge stops and time for recharge (I’m thinking from 20 to 80% which is what a lot of car manufacturers are suggesting for best battery life. I like the way you kept the video short and to the point. Would be nice to include some actual noise data to see differences with and without the roof rails and roof box. I would think to get the best comparison of efficiency without the rails and roof box would be to conduct the tests in the same conditions. Seems like a big decrease from 3.2 to 2.6 mi/kWH just adding roof rails, so I’m thinking weather conditions might have some influence?? Also, if you could summarize your results in a table format, that might be helpful for viewer (would be for me). Thanks again for a very good video.

[@hendriknoack6057]

Hey Zach, nice to see someone trying a roof box on an electric car. I had my bike rack on the rear of my EQV, and oh boy that consumption went crazy high. 1.94 mi/kWh. Normal consumption in the summer is at 2.59 mi/kWh. The bikes reach higher than the roof, and they completely kill the efficency. The roof box is way better in terms of efficency, which is no surprise.

[@Appalling68]

10:28 “Kum and Go.” The charging station is called “Kum and Go?” Are you kidding? Now that is too funny! 😂 LOL!

[@Macmonkey1000]

That's my preferred tactic, but my wife insists on cuddles afterwards 😸

[@kevinuher3415]

Thanks for the review. Conclusion, no EV for me 🙄 - till they make one that I can load 2-4 kayaks for a trip; My Prius V rocks this task, yes I lose 5-10 mpg but still ~250-300 mile range per fill up. Doesn't make any sense to get an $50k EV for local trips only. If I upgrade the Prius V will be with a plugin - but that's not happening any time soon

[@CSIG1001]

i will be getting the thule and omac roof rails . I just got a lease on a Hyundai and will be turning it in though in 2 years. Anyway i have free charging for 2 years :) i could care less about efficiency. Will be installing a curt toe hitch first though and will consider a hitch basket before roof rails

[@jamespaul2587]

Thanks for sharing Zach, however it would be more relevant to compare the results with the rails removed to the vehicle with rails and box installed. I suppose the rails are a pain to remove though, so many people will leave them on.

[@rick0842usmc1]

He said 3.2 miles per kWh with out anything

[@gothmog2441]

The rails are likely to significantly impair range, particularly at speed, as they will increase drag substantially. Not a good idea to leave them on, should remove whenever not in use.

[@jamespaul2587]

@@rick0842usmc1 yes, I heard that number, but a range test under controlled conditions with the same route would be more meaningful

[@jamespaul2587]

@@gothmog2441 agreed, however I believe some rails such as this are not really designed to be removed, that is unfortunate

[@_MrTV]

Thanks for the video I was about to go on a trip and will have dogs in the car so limited space inside and was wondering what the average efficiency loss would be for a few vehicles

[@omelvold]

Great and somewhat important test. In Norway, everyone and their mother use a roof rack to transport skis and excess luggage every now and then. Quite a few people even have the roof box mounted permanently. Often delivered by the dealer, painted in the same color as the car.

[@wolfgangpreier9160]

Not with EVs. With fossil cars it makes no difference whether it takes 7 or 9 liters. With a EVs its easily half the efficiency and double the price.

[@joniboulware1436]

That is the reason we have SUVs - so it can all go inside. And Europeans don't get our American cars...

[@wolfgangpreier9160]

@@joniboulware1436 True, Only Mexican ones. Built by Ford-Mexico.

[@atistiltins6163]

@@joniboulware1436 because in europe most people buy cars for the 95% of the situations they are in and the 5% situations where you do need a ton of stuff, you just get a roof rack or rent a microbuss or whatever, it is not that expensive, as just getting a really big car. Europeans are also not known, for buying stuff in huge bulks. For us having a huge car like a ford f150 raptor, while 90% driving is in the city is unreasonable (for the vast majority of people), to put it mildly - it would be like taking a WV golf to offroading level of stupid

[@godofdun]

ooo, great question to have an answer for!

[@thabangtlou9325]

Love the IONIQ5. Sad we have yet to receive this in South Africa.

[@ericm4840]

Good test, too, to see how much frontal area impacts efficiency.

[@tommays56]

The Most Surprising thing I have seen is how bad a loaded bumper mount bicycle rack effects a Model 3 range as it killed the rear airflow

[@kiwiramjet5625]

Forget the roof box, look at the size of those wheels 😳

[@frank26080115]

you should do another test with a queen sized mattress

[@teerex2231]

what about the overhang? that seems to create alot of pushback ir drag. (not sure of the correct term). since there was no weight in the front of the box, you could see it lift up.

[@TheAdventureAuto]

The efficiency with the box is pretty impressive, while the efficiency without it is not. And you guys must be really backed up on the vids if this is from Memorial Day. Wow!

[@jamespaul2587]

Yes, there was quite a drop in efficiency with just the rails added

[@summertyme5748]

You know for all of these range tests - we really just to see the Miles per Killowatt at 70 MPH. When you said 1.8 I was like 😵‍💫.

[@Jcewazhere]

I figure a little trailer would be a lot better than a roof rack. //hope you do test a trailer soon Easier to get stuff in and out of, when you don't need it all you have is a little ball instead of the racks, and it holds more. Charging while towing could be fun though, probably have to disconnect each time you charge. Been looking at getting one for my Bolt. 2.6mi/kWh at 70mph? Ouch. I just drove Canon to Pueblo and back doing 80 (sometimes a bit more, that speed limiter is probably a good idea...) and got 3.5mi/kWh in my Bolt. It wasn't as windy though. Yeah I guess 40mph wind would be like you driving 110 if it were a headwind, plus even a diagonal wind would force the car to slow down and speed up a lot. What do you usually get? //3.2 without anything on the roof? I was considering getting an Ioniq 5 a bit ago. I'd be happy just getting adaptive cruise control, don't need the fancy lane assist or 'FSD'. That 'biiig' 10% drop was probably just the guess-o-meter recalibrating. Also seemed less windy on the drive with the roof wart, this is why repeated testing is necessary. Thank you for doing at least this much though. I thought it was just pronounced 'tool'.

[@Stridermd]

What travel trailer do you have?

[@CryptoJoeTrading]

Great video! Those roof boxes are EXPENSIVE

[@robertkirchner7981]

That's the power of monopoly for you.

[@Wasabi9111]

Look for them used for much less. I got one used and it’s been great.

[@mrpogi23]

@@robertkirchner7981 not sure about monopoly, there are other good brands like Yakima, etc. Though they setup up their racks so u can only buy their branded accessories.

[@jamespaul2587]

Yes, but he purchased a high end model, you can get a more basic version at Canadian Tire or other stores, probably online also. It would be helpful to find one that can use removable roof racks as well to improve efficiency when not in use

[@ouch1011]

When you’re loading everything up to the roof (and on the roof) be aware of the GVWR. The Ioniq5 has an oddly low GVWR. It only allows for around 870lbs of passenger AND cargo weight, which is very easy to hit with passengers alone (especially in the US). Strangely, the passenger/cargo weight capacity in the Ioniq5 is *lower* than it is in my Bolt EUV. I suspect this is due to the brakes but not sure. The suspension doesn’t even seem to care when I load up nearly 900lbs of people (basically myself, my partner, and my parents), so I don’t think it’s that, but I wouldn’t be surprised if there was some sort of odd requirement where the friction brakes have to be able to stop the fully loaded vehicle multiple times in a row without regen, blah blah, and that reduces the weight capacity.

[@wojciechmuras553]

Yeah, but does anyone ever check it? I've only seen the police weigh semi trucks, and occasionally cars that were overweight to the point the rear suspension was bottoming out while stationary. I don't think anyone cares about GVWR... And it's not like in an airplane, where that could be a safety threat.

[@chunkychuck]

We need those backward facing ones like they have in Europe! They're much better. Bjorn Nyland did a comparison test

[@chrisness]

If you turned the box facing the other way, it’d be a lot more aerodynamic

[@Emily09876g]

They should test that!

[@NO_OPEC_NO_PROBLEM]

Great video, I think you need a 150mi test for each run to give better numbers.

[@justinfowler2857]

I'd love to get an ioniq 5. They're just too expensive right now. Guess I'll look at used later.

[@5290harp]

I wonder how the efficiency would be at lower speeds, like 65 or 60. But I guess since the electricity needed for a charge is relatively low cost the savings would only be a few dollars, eh? It's more about a range reduction I suppose.....

[@falconflyer317]

Have the exact same car. I already put the tow hitch on it. Installed it myself. Was surprised at how efficient it still was! A lot depends on the trailer of course.

[@jamespaul2587]

Yes, I expect a hitch box would be a more efficient way to haul cargo, as wind resistance would not be increased as much

[@legacytesla]

Efficient? It got 2.6 miles a kWh at 70avg with just roof rails on Eco mode... That's not efficient, that's terrible.

[@falconflyer317]

@@legacytesla You need some reading comprehension skills. I said that I was surprised how efficient MY car was when I installed a tow hitch and was pulling a trailer. I even talked about my trailer in it. if you want an efficient car, don't put a roof rack on it.

[@legacytesla]

@@falconflyer317 The Ioniq is not efficient stock with nothing on it tow hitch or just roof rails. You are the one who needs help with reading comprehension. The car is not efficient it is garbage. 2.6 miles a kWh is laughably bad with just roof rails.

[@falconflyer317]

@@legacytesla 🙄Let me guess, Tesla fan? I own an Ioniq 5. I get 3.5 miles per kWh on a bad day and higher on a regular basis. Your "omg such a bad car" isn't really working for you.

[@vitaliyleonov8958]

Damn, when we use public cherging station - EV not that cheap. Let's say charging cost 42 cent/kwh and gas cost 4.199/gallon. So 1 gallon = 10 kwh If your consumption is 2.6 mi/kwh - that's equal 26 mi/10kwh = 26 MPG Even if we take previous test result it will be 32 MPG Last year with 30cents/kwh and 5.499/gallon - EV looked much cheaper I did reallized that when I finished my vacation trip and calculated my charging spending. For 4k miles trip on Tesla Model Y LR I spent $525 (even though I put about 400 miles from hotel chargers for free)

[@Aaron-zx9rg]

Your calculations are a little off somewhere or else you have a very inefficient EV. I’ve done a few trips now and it’s never been more expensive than driving a gas car would have been. All my trips have resulted in significantly cheaper “fuel”.

[@vitaliyleonov8958]

@Aaron in UT speed limit is 80 mph and I drove 80 ! Also I installed all terrain tires wich also eat range. My average been somewhere around 360 watt/mile 😔. And it's depend on wich car you compare. It's less efficient than pruis but more efficient than almost any average SUV

[@Jcewazhere]

1 gallon is ~30kWh, not 10, but I'm not sure why you're comparing it that way anyway. 2.6mi/kWh at 42c per kWh would cost him 16.15 cents per mile. 42/2.6 =16.5 A 30mpg car at $4.20/g would cost 14 cents per mile. 20mpg would cost 21c/mi. 420/30 = 14, 420/20 = 21. My Bolt averages 3.5mi/kWh highway, or 12c/mi. City I get 5mi/kWh or 8c/mi even using overpriced DCFC. Home charging I average 3.5c/mi. However electricity was 34c/kWh at that station, so it cost 13 cents per mile. Only a 1c saving over even a relatively efficient gas car sure. Blame the greed of the corporations selling the energy at such a markup. Electricity at home in CO averages 13c per kWh. That makes it just 5 cents per mile most of the time even given that horrible 2.6mi/kWh. However however gas is dropping in price, it's down to $3/g in Denver so 300/30 = 10c/mi for a 30mpg car. EVs charging at home are still half the price per mile even for that juice guzzler, but for road trips depending on your MPG and mi/kWh you're not entirely wrong.

[@swanny6627]

How much did this box add to the cars height?

[@Arc_Logic]

Thanks for testing this so I don't have to!

[@dmunro9076]

I wonder if the lane centering was impacting range?

[@CERnoriVELO]

Never thought of this impacting an electric car. Thanks for the info!

[@_MrTV]

To be fair it impacts all cars 😂 just east to not notice in the gas cars cause filling up is so easy

[@saicharansunkara8921]

Yes. It does affect all cars but I think gas cars have very low efficiency to begin with to see much of an impact compared to EVs

[@ericcindycrowder7482]

@@saicharansunkara8921 exactly. Installing aero drags effects all cars, like you said. But since EVs are generally more efficient to start with, the aero burden is more apparent.

[@rocketsciencedesign]

On a side note ... is there really a petrol station chain called "Kum&Go"? Seems a little ... unfortunate?🤔

[@williamstanley2920]

So, what was your efficiency before mounting the Thule rack?

[@philorgneopolotin8762]

He said around 3.2 mi/kWh. Pretty big difference imo that’s not insignificant at all

[@tubelator]

Mmm nice. Thanks. But maybe one day also do the loop with just one person in the car. And see how 4 people in the car messes with the efficiency in any way. 😊

[@omelborpon3159]

The bars themselves, mounted without the box, will add significant aero resistance.

[@wolfgangpreier9160]

Maybe we could integrate the bars into the car and make it flush with the ski-box? I guess then the car is called a van. Right?

[@leonvdm]

13% in this case according to his data

[@kal1nas]

Wait so if without the roof rack and rails it’s 3.2 but with them it’s 2.3 isn’t this almost a third less efficient?

[@bruceryan5919]

Does anyone make a box that has an airstream rear end?

[@ianburton5624]

You probably don’t have this use case in Colorado but I would be interested to see how the efficiency drops with 3 sea kayaks on the roof. That’s how I have my car loaded up most weekends and I’m often driving 100 - 130 km each way to places with no rapid charging facilities.

[@jamespaul2587]

That would be interesting Ian. I expect with the additional wind resistance, the range impact would be substantially higher than with the box, perhaps twice the reduction in efficiency of the box over the rails alone, especially in windy conditions

[@wolfgangpreier9160]

You need a Lucid with the built in solar roof. Or you wait for the cybertruck with the solar vault cover. Best idea would be to wait for the Mercedes E-Actros, Then you can put your boats, dogs, cats, children and half of your house inside and don‘t care for charging facilities. Don‘t buy the Tesla Semi! Bad panel gaps. Really bad panel gaps…

[@-Jethro-]

I wonder how this compares to a hitch-mounted carrier rack.

[@stang393]

Hitch should be less

[@poxcr]

The weight affects efficiency as well... Testing 'no box' vs 'loaded box' is not an appropriate comparison. How can you tell the performance loss was due to the box and not the extra weight?

[@ericcindycrowder7482]

Good video but your test was flawed. Need to compare the installed box compared to a baseline WITHOUT the bars attached. The bars alone are going to drop efficiency with lots of turbulence and separation on the roof.

[@dreamsofhaegum]

He did, and gave the figures in the summery at the end.

[@leonvdm]

box vs only bars (2.6-2.3)/2.3*100% = 13% increase in energy use box vs nothing (2.3-3.2)/3.2*100%*-1 = 28% increase in energy use. So remove it when not using it! not really that much of a difference?!?!? well it think 13 or 28% IS that much of a difference

[@burntheelastic6556]

I would imagine there would be less efficiency with a whole family in the car with the rack

[@SimonSedgwick]

Passengers and even fully loading the trunk doesn’t affect the efficiency as much as you would think. You’ll find a drop of less than 20miles on the range.

[@mhamma6560]

28% reduction in range is actually quite a big impact. 3.2 clean to 2.3 w/ the box, that's far more than a minor impact. What's worse is that you've had a 19% reduction in range with just the rack system. Wow -- and you're leaving it on? Your battery just had 1/5 of its capacity vanish. Consider a different vehicle if your needs are such that more than 1/4 of your 'road-trip' vehicle's range took that much of a hit. Besides, the ionic is pontiac asztek levels of oogly.

[@lplt]

wonder how much of the difference is the weight and not the aerodynamics

[@Matt-dx3wo]

very little

[@ouch1011]

Basically none when driving at steady speeds (like the freeway)

[@Nomanmirza]

You install the roof box wrong way! turn your roof box other way around and you will safe lots of juice. always follow teardrop shaped

[@legacytesla]

2.6 miles per kWh with just roof rails on in Eco mode? That's crazy, why is the ioniq 5 so inefficient? My 2022 Lightning is massive by comparison and averages 2.4 at the same speed and my Tesla Model Y blows that thing out of the water.

[@danielgagne2912]

Not a very thorough test guys. Drag caused solely by the rack on the first test??? not exactly a control. Then, how much of the surplus energy consumed is because of the weight that's in the thule?? ...Not impressed

[@darylwilliams7883]

Not surprising. My roof box destroyed gas mileage in my regular car.

[@otternng]

You should check out the Calix Aero Loader that's made for EVs. Link to Björn Nylands video about it: kzbin.info/www/bejne/kGGzZ5xnjtiaf6s

[@chunkychuck]

As far as I can tell they don't sell those here! I really want to see more in that style.

[@otternng]

@@chunkychuck oh, bummer!

[@williamshelton9688]

Would you be less cooler if you turned your hat around ?

[@AllPowa287]

At this point just get a truck lol

[@Aerostealth]

I watched your video but I just don't have enough bread crumbs to make it back to reality, so help me out here. In what reality is a 28% decrease in efficiency a win? You should go back to your aerobrake company and ask to exchange your box for a sharp stick in the eye. FYI, this is not how you test for efficiency at all. You should have topped off back to 80% after each test, recorded the kWh, and then did the math.

[@lancastergerard]

2.3 with the box 2.6 rails only 3.2 no box or rails Now you know why ev’s for focusing on aerodynamics

[@stang393]

Right, but for him to say "not to bad" is i guess subjective, but to me kind of misleading...thats almost 1/3.

[@ApteraOwnersClub]

@@stang393 that's a huge drop

[@cavemankiwi]

@@stang393 Yeah it not is not the description I would use. F#$king horific would be my choice. I assume in a larger vechicle like a R1S the drop would be less. I have a R1S on order and anything like this level of drop would make Tahoe ski trips form the Bay Area quite a bit more painful.

[@stang393]

@@cavemankiwi my gut says it will be just as bad on the Rivian, as we know towing cuts range in half. We also know that weight isn't the cause, its drag. I would think a hitch mount box would be the better one.

[@LearningFast]

2.3 mi/KWh is horrifically bad. That is 435 wh/mi. My Tesla Model 3 Performance has averaged 268 wh/mi for almost 9,000 miles now. Even a Model X would get way better efficiency than this.

[@ouch1011]

Comparing a Tesla that’s shaped like a Prius compared to an SUV with a giant wart strapped to the top is not exactly an apples to apples comparison. A Model 3 with a gigantic roof box on it would also have horrific efficiency. He was also driving on a day when there was 20mph sustained winds and 40+ mph gusts. Probably not a good day for efficiency testing.

[@wolfgangpreier9160]

@@ouch1011 My Model Y takes 172Wh/km or about 275Wh/mi but i drive about 80% on the Autobahn. Of course with a roof box i guess it would take about the same. My Model 3 uses even more energy because its wifey‘s car. What can i say.

[@user_z01]

Kinda ruined the video there at the end by blatantly ignoring the math which is illustrating massive difference in range potential.

[@robertt1336]

Many posts suggest mounting backwards so to prevent tail drag with blunt end. Are there any EV boxes with thin tail ends on both front and rear? Could we get a range test with a hitch style cargo box also? May help with drag/range loss, especially in winter 🥶 🪫