I am interested in the impact of cold weather on EV range of the Model S and the reasons why cold weather has such an impact on EV range. The range calculator at Tesla's web site seems to be extremely optimistic--I don't think I trust it. I do not have a model S, so I am providing data I observe for my car (Ford Fusion Energi). Below, I have plotted kWh/mile I have observed for my 8 mile EV commute to work vs. temperature. I do not use heat or air conditioning for the vast majority of the trips. During the winter, I precondition the car before I leave so it is warm when I leave. The commute is only 12 minutes so it doesn't cool down all that much when it is below 0 F outside. There is no heater for the battery in the car, so the variation in kWh/mile is solely due to temperature, weather, wind, and traffic (and not the use of heating or a/c). It is a city commute with posted speed limits of 55 mph. As you can see, when the temperature is 80 F, the kWh/mile is approximately 0.236 kWh/mile. When it is 0 F, it is approximately 0.320 kWh/mile. It requires 1.36 times more energy for my commute at 0 F vs. 80 F due to the colder temperature. This is far more than I would expect due to greater air density alone (1.15 times greater at 0 F vs. 70 F). There must be other factors coming into play than denser air. I suspect that there is a lot of internal friction in the car at cold temperatures, i.e. wheel bearings, transmission fluid, gears, etc. When I first start out in the winter, it takes more than three times the power initially to propel the car than it does in the summer. Since I am travelling at low speeds, most of this must be due to this much greater friction in the winter. Has anyone done a similar analysis for their commute to work in the Tesla, i.e. kWh/mile vs. temperature. Ideally, it would be without the affects of heating and a/c or the battery heater.