IMHO comments like this are much more valuable with some numbers.

The linked figure[0] and associated paper report that efficiency peaks for EVs at around 20mph and then the cost per mile increases roughly linearly, by about 25 watt-hours when the speed increases by 10mph.

Please excuse the archaic units.

[0] https://www.researchgate.net/figure/ehicle-energy-economy-at...

The Tesla Roadster is an absolutely ancient EV.

This.

And it is true of petrol cars as well. In my old clunker going from 110 km/h to 120km/h is a 9% speed increase but nets about 15% extra fuel consumption.

Is this with the windows up or windows down...?

Yes.

And much more than one would intuitively think.

I just finished a long drive for summer vacation. Driving through Denmark (completely flat) at 130 km/h would absolutely wipe the battery, would be surprised if I managed even 350 km on a full charge. Driving over the mountains in Norway however, from 0m elevation to over 1000m and down again, at slower mountain roads (max 80 km/h), yielded almost 500 km on single charge.

I did not expect flat+high speed vs hill-climbing+low speed would be that dramatically different.

Air resistance is proportional to square of velocity. That goes up pretty quickly!

And the power required to move against the air goes up by the cube of speed (as you multiply the resistance times your speed itself.)

I imagine that regenerative braking has a role here too. When you're going downhill the battery can recharge itself to some extent.

Yes, but Tesla goes out of their way to advertise how fast their cars are, so you think they'd expect and factor for this kind of driving behavior.

graphs:

https://forum.abetterrouteplanner.com/blogs/entry/22-tesla-m...

https://forum.abetterrouteplanner.com/blogs/entry/9-tesla-mo...