The pack loses about 3 ideal km (400 Wh) every day it sits idle, probably mostly power for the microprocessors that control and monitor the car (VDS etc.). In normal charging modes it will top the pack up daily.
In cold weather, while plugged in the car will heat the pack to keep it just above freezing. This heating is disabled if the car is put in Storage mode.
Reportedly in really hot weather it may run the A/C to keep the pack cool, but I've never seen that (we get hot weather but not THAT hot apparently). Of course it runs the A/C during charging to cool the pack.