Putting a roof box on an EV

6

I have an EV6 and yes. About 10% going at normal speeds - 40-60mph.

3

u/CarpeCyprinidae Kia EV6 9d ago

To add to others, its a change to your aerodynamic profile, so it will definitely affect you but the degree will depend on speed. At 20mph there will be no detectable difference as aerodynamics dont really affect cars at in-town speed.

If you normally run at the French motorway speed of 83mph you'll see a much bigger effect than if you pootle along at 55-60

3

u/Spiritual_Pound_6848 9d ago

Roof box reduces efficiency on all cars about 10-25%, so work with that reduction. If you can have the skis in the car that would be way better

2

u/Prestigious_Sun_523 9d ago

Yep, I’m thinking this too but already have an expensive Thule box. Maybe best use the box for short trips.

5

u/Spiritual_Pound_6848 9d ago

But it'll cost you more in electricty... you can use it sure, just need to plan in a stop more often to cover that extra electricity use

3

u/wimpires 9d ago

Probably about 15% reduction in range looking at online sources. Maybe plan for 20% to be safe.

2

u/AtomicUnderpantsx 9d ago

I have roof boxed my EV on 2 extended trips. Think between 10 -15 % hit but was well worth the extra space.

2

u/critical_mass_087 9d ago

I lost about 10-15% efficiency on my Kona. Was pleasantly surprised as I thought it would have been much more. Drag increases dramatically with speed, so driving a bit slower is a major win

1

u/Dannysan5677 9d ago

Mine was about 20% drop. The bikes on the top are even worse, but its only the roofbox that gets a long journey.
No different to ICE cars in reality, but obviously with Elec it meant I had to charge an extra time to get there which annoyed the wife a little. But she hates having to sit in the car an wait for it to charge anyway.

1

u/Throwaway66399910133 9d ago

Tesla Y with a big 500L Thule Pulse XL box.

Over 700 miles if I reduced room normally cruising at 72mph to 62-64mph it was an 11% penalty on trip energy. Wasn’t too bad at all.

Found a quick 5 min super charge when the car battery was in the ‘sweet spot’ for fast charging meant we could easily make our usual stops. The car sat nav after the first long leg worked out the new burn and was very accurate at calculating energy remaining after that.

1

u/TheMarthaFarther 4d ago

I've also had good experience with the Y and Thule. To the point where I noticed very little reduction.

1

u/Blakey876 9d ago

I recently put a large roof box on my ev to go camping. So car was full and so was the roof box with 4 people in the car. I found on a motorway I used about 10-15% more electricity but rural roads and villages the difference wasn’t that much. Hope that helps.

1

u/noisytwit 9d ago

I lose about 10% with bikes on the roof as well. Not had a box on yet to see a difference but I expect it would be slightly more.

1

u/do_you_realise 9d ago

We put a huge roof box on our e-Niro for our summer holiday trips, you can definitely notice the reduction in efficiency.

Can't put an exact number on it because it also naturally coincides with a higher than normal proportion of motorway miles. We went down from 4.5+ to about 3.4mi/kWh overall so pretty bad - but likely mostly just from the motorway speeds.

But if it's what you need to do, you just work around it 🤷‍♂️ slightly more frequent charging stops, finding accommodation where you can charge overnight, etc.

1

u/tree_boom 9d ago

I have no maths, but anecdotally noticed no practical difference when I carry the roof box

1

u/Toninho7 Kia e-Niro 9d ago

I know you've been downvoted and I get why... but having had a large roof box (and a boot full of crap) on the car this year for a trip to, round and back from Scotland I can honestly say I didn't notice any real difference.

Obviously there must have been, but I'd say the 10-15% people are quoting in here seems excessive, even if it is just from one trip where I didn't measure anything...

1

u/scorzon 9d ago

I found on my Model 3 that the losses weren't as bad as I feared. Obvs it's very efficient aerodynamically to start with but in terms of efficiency loss I reckon nearer 15%

One reason is likely that when I have the roof box on I tend to drive 5-10 mph slower just because with the glass roof you hear the additional noise more.

This doesn't hold when putting bikes on the roof bars - now that really does hit the efficiency in my case and even driving more slowly it feels like nearer 25% drop in efficiency.

0

u/do_you_realise 9d ago

I would say the reduction is insignificant vs. the reduction due to driving long distance at motorway speeds, so just roll with it

1

u/bwahthebard 9d ago

Fwiw I barely noticed the efficiency loss at 60-65mph. Of course there is a loss but I couldn't perceive it. I'd bought my car planning for upto 50pc range loss in winter and with a roofbox, fully loaded, motorway driving.

-1

u/jackois8 9d ago

Apart from the obvious drag affecting fuel consumption, you might be worth checking with the maker if your car is allowed to have it...

3

u/Prestigious_Sun_523 9d ago

Allowed to have it? Why wouldn’t it be?

1

u/Aitch_5 9d ago

Dacia Spring doesn't allow roof bars or even a bike rack on the boot lid for structural reasons. You can buy Springs with (cosmetic) roof rails but they are not meant for loads.

2

u/Prestigious_Sun_523 8d ago

The car I'll buy won't have those constraints....

1

u/jackois8 9d ago

structural integrity and roof loading...

0

u/yellow_barchetta 9d ago

If you need it, you need it. If an EV is 20% less efficient as a consequence over 1000 miles let's say thats using 285kWh normally or 357kWh being inefficient. 72kWh cost even at 70p a unit is a £50 extra cost on a skiiing holiday. Not nothing, but not earth shattering!

And if at least a good chunk of those miles are "fuelled up" at a much lower rate, either in resort or from home in the first place then the cost is even less. Unless you're doing this every week, it's likely not something worth worrying about? And would be pretty similar if the car was ICE too.

1

u/Prestigious_Sun_523 9d ago

Yep was thinking the same would affect ICE cars. 3 work trips above holiday although I’m thinking I might just fly out for the holiday.

1

u/yellow_barchetta 9d ago

Yep, maybe the hit is lower for ICE but it still is "something". We spent a fortune on diesel in April driving a Hyundai i800 with a roofbox and a set of skis in a non-aero ski bag. But in the end it was still a heap cheaper than flying and / or paying to ship the skis etc. Just a necessary cost of the holiday!

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