What I've heard on this angle is that the Tesla maintains the batteries at a safe operating level overnight to enable the owner to drive at any time. They could implement a storage mode that allows the batteries to drop below operating temperature while staying above damage temperature, but their software does not yet do that.

Tesla has a bit of the Apple approach to software, where they intentionally limit the number of software options to not overwhelm the user. This may change as they continue development, but it's where they are now.

Mostly correct, but I remember standing outside my 5th grade classroom window waiting for the teachers to unlock the door. At that time the school doors were only unlocked prior to class starting if there were blizzard conditions, not for cold. The classroom had a thermometer on the window that read -50C at the time. The only reason I remember it was because it was the first time I realized -40C = -40F.

http://en.wikipedia.org/wiki/List_of_Minnesota_weather_recor...

Note to self, avoid living in Minnesota during the winter :-)

Hah - someone in the first HN discussion about this was complaining that it was unfair to complain about the Model S becoming less efficient at low temperatures because ICE cars did too, and as I recall his definition of low temperatures was -50C.