Just had my first real winter driving experience with my Model S. For those short on time, the quick summary is this:
1) Heat the car well before setting out.
2) Separate the wipers from the windshield before starting the car.
3) Don't open the rear doors until the car is fully heated.
4) Expect to get at most 90% of the estimated range at freezing temperatures.
The longer description is this:
The purpose of the trip was to drive 278km to the Toronto Tesla service center to get winter wheels and tires installed.
I set out with the car unheated, on clear roads, with the outside temperature at -2C, on my 21" wheels and Continental tires. Problems started before I got out of the driveway. In freezing temperatures the windows can freeze to the seals at the bottom of the window. Frameless windows lower slightly when you open the door, and slide back up when you close it, but can't do this when they're frozen. I opened one of the rear doors to get something out of the back seat, popping the unlowered window out of the top seal in the process, and then couldn't close the door. After a certain amount of prying with my fingers, I separated the window from the lower seal, lowered it a bit, and was able to close the door.
I got in, stepped on the brake to start the car, and heard and ominous thumping and grinding from in front of the dash. Turns out the wipers were frozen to the windshield and the "auto" wiper setting tried to start them wiping. The wiper motor working against the frozen blades caused the linkage to pop off the motor under the hood, rendering the wipers inoperative. I didn't need the wipers anyway and was headed to the service center so it didn't matter in that particular situation.
Total distance was 278km and I left home with a full range charge and estimated rated range of 405km. I drove 100km/h the whole way, with the heat off (outside temperature 28-34F), and arrived with a remaining range of 60km. I.e., almost 65k less than I would have expected. The range estimates had been uncannily accurate during the summer, so I think the relevant winter factors that threw it off were:
a) Energy required to heat the battery at the start.
b) Higher ride height, and reduced aerodynamics, introduced with software update 5.8 to avoid hitting road debris.
c) Colder (hence denser) air. A drop from 25C to 0C produces ~12% increase in air density and proportional increase in wind resistance.
d) Occasional, though minimal, use of defogger and seat heater.
At the service center I got the new Aero wheel / Pirelli Sotozero tire package, got the wipers fixed, and a bit of a charge. I headed to the Yorkdale mall for another 3 hours of charging before setting off on the remaining 258k drive home. An hour into the charging I noticed the car was using only 58 of the available 80 amps. I adjusted it to use 79/80, with no apparent increase in the charge rate. So I stopped and restarted the charging. The rate jumped from 56km/hr to 74km/hour. I suspect, but am not sure, that it may have been using the lower rate because the battery was cold when I connected it.
I was curious what difference the Aero wheel and 19" tire combination would make to the range. I set off on the 258k return trip with a warm battery and car, and an estimated range of 275k. Not a lot of buffer, but there were places to charge along the way if necessary. I drafted a truck almost the entire way, used no heat except the occasional defogging, and arrived home with 10k to spare, having averaged ~182kW/km. The same driving with summer wheels and tires (and lower ride height) uses ~165kW/km.
Your mileage may vary, but I'd definitely expect 10-15% less range than you get in the summer, and I'd recommend unfreezing the wipers and windows before using them or opening the doors.
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