I read that model S has a simple heating element to heat the cabin. Nissan Leaf have now a reversed AC called heat pump. Is Tesla going to use a heat pump that can reduce by 66% the energy required to heat the cabin ? Instead of 6kW heating element it would use 2kW heat pump to bring 6kW to the cabin It's current technology to reverse the AC cycle to heat. Many houses have that as well as Nissan leaf. It would help range in the winter.