The colder it gets the worse the losses it seems I am up near 30kwh/100 for many of my journeys a mixture of prewarmed and not whereas in the summer I would be down to 21 or lower. I wonder if over a longer trip it might even out a bit more as the cabin is warm and the heating starts to use less energy not least because we heat it with our presence . So I am also looking at around 30% loss. Whether that is the lowest as the car performs the same at 0 or -2 as I have been driving in as at say -10 I do not know but the car sells well in Norway where the temps are a lot lower. I wonder if cold weather performance is like battery charging with a levelling off at either end of the curve so once it gets cold a point x its performance does not degrade at y or z but improves considerably if it is at point m or n. Sorry I am not scientifically trained so my explanation may lack finesse!
We did not have as a long a spell of cold weather here in north west France last year so I do not have other winter stats to compare it too. The other issue someone else posted on another thread is the effect of the tyre pressure reducing in the cold, I know as a cyclist low pressure really makes a difference and possibly in the electric car it may also have an influence. I set mine at the 280 a couple pf weeks back and was getting 290 on a run today just 280 so they will be starting lower. However we must not forget ICE are the same they too use more fuel in winter it was just people were not so focused on rage so specifically as we are with electric cars, and many do not really register how the mpg drops as they do not really monitor it. Certainly my c and e class gasoil mpg went up in winter.