On my 72.4 km, I used no heat at all, just preheating before leaving. The seat heater is fine to heat what is on the seat (hic) but not of much help for my cold feet. So I had cold feet on the return leg. Longer trip would need some more heating in minus 8°C temp., even more when It will go down to minus 20 -25°C in january.
It seems to me that in addition to the cold weather effect on battery, bearings of the car, and air having more density, the fact that the car is not broken in might give less autonomy ? What do you think ? Did you see gradual improvement in the first few thousands km ?
One final note. When recharging after turtle, it took 20+ hours. What surprised me was the cruising range indicator (Gom meter) indicating 151 km to go, never that high before. It tells me that the past drive data it uses is short, I mean not taking into account the whole 72.4km but mainly the return leg that was done at low speed more down than up. The worst GOM I have seen was at the dealership. Full charge gave projected autonomy of 62 km. It sure had been driven very hard before by the company who had it on trial for his employees for 2 days.
Last friday going out of the dealership (first ride) with 15 bars out of 16, I was home (93km) just before turtle. T° +4°C, no heating, no headlight except last 25 km, and nice tail wind. I was driving conservative but following speed limits on secondary roads ( 90kmh, 50 kmh in town). It seemed to me a little short autonomy, considering the tail wind.
Note: It is a little difficult for me to translate fast all these °C to °F and km into Miles, but if you prefer I will do my best.