To add another data point, here's what I learned last night, driving my regular Thursday evening route, when the OAT was between -3 deg. F. and +5 deg. F; in more moderate weather, with temps between 50 and 80 F., I usually make the round trip averaging about 300 Wh/mi. Roads were mostly drive pavement with a little dusting of snow later in the evening. Winds were light.
Mine is a Model S Sig, VIN00118, non-Perf, 85kWh, riding on 19" stock wheels with new Michelin X-Ice Xi3's all around. I started around 5:30pm when the OAT was +5 F and the car's OAT gauge (in the garage) read +41 F. Rated Range was 242 miles at the start, following half an hour of last-minute charging and preheating the cabin. I kept the thermostat at 64, used the blue Defrost setting mostly, with occasional bursts of red High Defrost. My car has the old style vents and fogging of the left side of the windshield and the driver's door window was an issue throughout.
The first leg of this trip is on E-470 a lightly-traveled divided highway (it's way out of the way and has steep tolls, but driving it is so much less crazy-making that I usually just pay the tolls and accept the wear and tear on my tires) with gradual climbs and descents, with the low point being about 5100' elevation and the high point about 6100'; I had the cruise control set for 74 most of the time, though there were traffic slowdowns the last five miles or so. The highest average I saw was 440 wH/mi about 35 miles into the leg as I crested the highest point of the route. Totals for the leg: one hour travel time, 57.9 miles driven, 82 miles Rated range used, 23.7 kWh consumed, at an average of 410 Wh/mi. The temperature dropped to -3 F. at one point, but hovered around zero F. most of the time. Normally at this point in the trip I'd be sitting at 330-340 Wh/mi.
A little less than four hours later I emerged from rehearsal to find a light dusting of snow and the car's OAT reading +5 F.; as soon as I started moving it dropped to -1 F. Notice that the car 'lost' 8 miles of Rated range while sitting unplugged for that length of time. I did turn on the cabin heat remotely, about 15 minutes before driving.
The second leg is much shorter, because I go straight up the gut through Denver instead of taking the long way around. The first ten miles or so are 35-45mph, stop-and-go on city streets; once on the highway it's 60-65mph most of the rest of the way home. I got home 45 minutes later having consumed another 13 kWh and averaged 'only' about 360 Wh/mi for the leg (it's the speed, stupid!), for a trip total of 93.2 mi, consuming 135 Rated miles of range and 36.7 kWh, at an average of 394 Wh/mi.
If you accept my statement that this route normally averages right around 300 Wh/mi, this cold-weather trip consumed about 31% more energy. A note on regen limits: even after preheating in a 41 F. garage, I started out with the regen limit at about 30 kW; it slowly increased until disappearing completely about halfway through my first leg. After four hours of cold-soaking, the regen limit was about 20 kW and never completely went away, rising to about 40 kW by the time I got home.
In summary, then: Chad_S's
trip-planning, no-headache recommendation to limit legs to 177 miles max between charging stops in an 85 is golden...unless the weather's really, really cold; really, really snowy; and/or with high winds or large elevation changes. I would have made 177 miles last night, but just barely. Of course, I didn't start out with quite a full Range charge, but the roads were mostly dry pavement and the winds were light.
