Running a preheater loop for the heat pump from the systems than need to be cooled, inverter and motor that run better cold,and other optimisations could likely supply cabin heat with very little battery draw, solar pv blended into the exterior could zero that out on an average basis,but 40 below is nothing to play with unless you know exactly what you are doing, even if they say it will still work.

https://electrek.co/2026/02/05/first-sodium-ion-battery-ev-d...