So far so good. Zero degrees in Dorset, and my three Haier units are keeping the house at 70 with no issue. Installed this past summer. I turned on the oil burner this morning and set its thermostat at 64 as a fallback, but the circulators have not needed to come on at all. House is about 2600sf, but about a third of that is a basement room which I'm not heating. It's dropped to 51 down there today. 3 sides of the basement are below grade, so it's fairly stable down there.