Thanksgiving morning, we (my wife and 6 year old son) set out in the new S85 (grey/tan/pano/air #18055 v5.8) for a round trip from Concord MA to Saratoga Springs NY for Thanksgiving dinner and family visit. We usually make the ICE trip by way of I-90 West and I-787/I-87 North which is fast but longer distance of about 200 miles. Forecast was for temps between 24-28F and winds from the west (headwinds) at 15-20mph with even stronger gusts. With the combination of cold, strong headwinds, and longer distance, I thought it was quite likely we might not make that distance in the Tesla. Alas, we are still waiting for the Sturbridge area and Albany area Super Chargers which were promised for the "Summer" and now the "Fall" but don't yet exist. With a Super Charger, this would have been easy. That's all I want for Christmas. Instead, we went for a shorter but slower route out Route 2 to I-91 into Brattleboro VT, then 9 west up and down a small range of mountains (road above 2000 feet) to Bennington VT and assorted back routes into New York state to Saratoga Springs. Distance was 172 miles to our Thanksgiving dinner. Average speed was 49 mph, and we consumed 215 rated miles (starting with a 265 rated max charge), 59.8kWh, averaging 348 Wh/mi arriving with 50 rated miles on the odometer. After dinner, we drove another 10 miles or so to the Hampton Inn in Saratoga Springs, a nice hotel with a 2-port Charge Point station in their parking garage. It was colder out (low 20s), the battery was cold, and we consumed about half of the remaining range (25 rated miles) to make the 10 mile trek. The Charge Point charger worked great and successfully charged to 90% overnight. We spent another day with family in Saratoga Springs, gave a few spirited rides in the Tesla, and headed back to the hotel for a second night recharging to 90% in the early evening. At 6:30AM, I set the charge level to max with the iPhone app. We got up an hour later, walked into town for coffee and a light breakfast, and the car was ready to go with another 265 mile max charge for our return trip home. The return was 185 miles over nearly the same route. This time it was less windy but very cold, about 16F when we left and it was still down around 18F through the mountain pass in Vermont, warming up to about 28F by the time we got home. Average speed was again 49mph, and we consumed 231 rated miles, 63.6kWh, averaging 343Wh/mi and arriving with 35 rated miles on the odometer. Both ways, I set the climate control to "Range Mode" and "A/C off" but otherwise we kept the cabin temperature set to 64-65F and made use of heated seats. Might have been a little cold at our feet but tolerable. We were driving with traffic, 70+ on some parts of I-91 and Route 2 but slower through some small towns and mountain roads. All and all it was a successful trip - the route we chose took a little longer than our usual route, but was also quite scenic and enjoyable. The Tesla performed flawlessly. Some quick geeky analysis: If I use the "flat ground" calculator on Tesla's website http://www.teslamotors.com/goelectric#range and punch in 32F (lowest temp), "Highway" driving, 50mph (average speed) and heater on, we get a range of 268 miles. This trip and my previous trips with v5.0 firmware suggest that rated range is linear between a reserve of 12kWh and max charge of 85kWh, so this is equivalent to 272Wh/mi. Our route had a lot of ups and downs, and looks like a total of around 10,000 feet each of ups and downs one way (using evtripper.com). Using a 64% regeneration efficiency (I read somewhere on the forums that this was a good number derived from 0.8^2) and the potential energy of 5,000 pounds (car plus passengers an luggage) at 10,000 feet divided by distance traveled works out to be about 57Wh/mi. So adding that to 272Wh/mi we get 329Wh/mi. Our actual consumption was 5% higher at 343-348Wh/mi. I'm guessing that this difference is a combination of the colder temperatures and strong headwinds in the one direction and the even colder temperatures in the other direction. So, I would conclude that you could use the calculator, account for elevation changes (at about 700Wh/1000ft), and add 5% would be a fair estimate of consumption at 20F temperatures. The Tesla calculator shows about an 8% increase in consumption going from 50F to 32F, so this appears to be in the ballpark if you extrapolate 32-20F. I like evtripper.com, but it only shows correction for temperature down to 52F, and extrapolating (about 1.2kWh/10F) was about 20% optimistic (looking at the return trip where wind wasn't likely a factor), but it does account for elevation changes (and that's where I got the elevation data for my calculations).