As per TexasEV, the trip meter doesn't show all the energy consumed from the battery, but I believe it does a good job of showing the energy productively transfered into useful stuff like HVAC, battery heater and propulsion. If I am right then the difference between energy put into the battery (~77Kwh), and energy that was available for useful stuff (~66Kwh), is simply the inefficiency of the battery at lower temperatures. When the battery cells are cold the internal resistance is higher so this internal inefficiency is down to the battery chemistry actually holding onto some of the energy as heat energy within each cell (without going anywhere near the BMS plumbing). The driving was pretty much worst case for this for 4 reasons 1) I'm guessing there was a 'cold soak' start 2) The driver is was very economical driver on this trip which keeps the motor and inverter from generating much heat 3) The two 2 hours stops allowed the battery, and all the materials and air in the cabin to cool back towards 5degC 4) Teslas have a 'cold pessimism mode' that undestimates remaining range (although zero should be zero I suppose) when leaving a car in the cold conditions, and there are accounts of the range coming back up a fair bit once the car is driven again (even without charging).
I presume that, when your friend put the car in park at the end of that, he got the very polite message "There will be significantly less energy available from your abttery if it gets colder. We recommend charging now". This is from experience recently where I made a range stretching return trip back to Wales in cold weather to make my daughters birthday
So in summary Jan, tell your buddy not to worry, for a single trip in those temperatures, 270km would be the likely range. If that them gets far enough to see beautiful Prague this Christmas then plug in, have a shot of Bechkerovka, and relax
