Heat source here is a freestanding 30/K btu propane stove along with a single register 30 amp Gree mini split system. Amazing how the mini split can still put out heat at 40 below. Toasty...Woke up at 4 am and it was 6 degrees here. I've been on this place for 22 years and this is the coldest I can remember. The wood stove can barely keep up at these temps so we've had to turn on a couple of space heaters.