Well, had quite the time on Sunday with thos sub-zero temps and breeze..HAd the house up to the 73 mark and struggled to keep it there I tell you even with being home all day and reloading..Although, I first re-loaded from the night before at 7am (temp 66) got the house up to the 73 degrees and didnt re-load until 2ish, house only at 70.. 7 hours of maintaining a house temp on a windy, zero degree day aint bad I would say.