Will we have any remaining battery charge left when we return?
Assuming sentry is off and the car sleeps, it probably loose about 1% per week. (Tesla says to plan for 1% per day, but thats a huge margin to the real consumption when parked).
Both my M3P ’21 and my MSP ’23 use roughly 1% per week.
It is the same in cold weather but the displayed SOC will fall more the first day.
Tesla consciously displays a lower SOC when the battery is cold. How much depends on the battery temperature but you can se 5% less than the real SOC if it is well below freezing. This ”drop” will not continue when the battery has cooled down, so you mostly ”loose” these percent the first day, then there is no more such drop (except if it gets colder).
All of this energi still is in the battery, so you will get it back if you warm the battery.
(You can see the displayed loss due to cold battery as a blue part of the green charging level.
Tesla states you should avoid to leave the car below -22F (-30C) for more than one day.
I have had it several times standing > one day below -22F but then I have activated charging which heats the battery. Actually mostly only let it heat and then cut off the charging.