I could be completely wrong about this (we don't use the heater much here in Texas anyway), but wouldn't running the car initially in HV mode (running the ICE until the engine reaches its normal operating temperature) provide good cabin heat by calling up heat from the engine circulation instead of (or maybe in supplement to) the resistance coil?
I tried searching the forums for this but didn't get an answer: - Does remote climate in the winter (Canada ) when plugged to 240V charger, turn on the "rear defrost"? And what about the seat heater?
By "efficient" I meant we don't have to yoyo the heat settings, which is particularly important for Missus Clarity, plus it seems to have a minimal impact on gobbling EV charge. Most of the time we get a few more EV miles than the GOM instead of losing miles to temporary 87 degree heater settings.