Here's a diagram of the Tesla Model S's heat/cooling system. It's taken from a leaked picture of the engineering tools built into the infotainment system, which is a scary concept once you think about it:
The car needs a substantial amount of both active heating and cooling in order to enable the batteries to both charge at all below 0C and to charge and discharge extremely rapidly when attached to a Supercharger or under heavy acceleration.
http://i.imgur.com/TOUXlWM.jpg
The car needs a substantial amount of both active heating and cooling in order to enable the batteries to both charge at all below 0C and to charge and discharge extremely rapidly when attached to a Supercharger or under heavy acceleration.