The biggest deal, I found, was stop-and-go city traffic. Heat is provided by the minute, no matter how fast or slow you go. In a city with basically no expressways and a plethora of traffic lights, even on main roads, I had a 12km commute that averaged about 25 minutes. At that rate, I used 3 to 4 km for each km traveled. On highways, doing 100kph, it was more like 1.5 to 1; and of course, once the car is heated, so it';s a longer highway trip, the cabin heat is less. On a long road trip (120km each way) doing about 105kph at -5C, cabin at 18C and one seat heat on, I found it worked out to 1.4k used for each 1k traveled. Plus I can tell by the melted snow around the front camera on the windshield - I bet sentry mode is not a good idea at really cold temperatures.
OTOH, my BMW at -30 also will warn that the battery was low and some electronic functions had been turned off.
The difference was, I have a NEMA 14-50 plug in the (insulated, unheated) garage for my charger, so I started every day with a "full tank" (80%). Plus, with mostly city driving, my indicated (calculated) range quickly dropped from 400km for a 80% charge to about 360 to 270 depending on how much highway I've done recently. If you have a longer commute, you may want to set the nightly charge to 90%.