It's 10 deg F here now and the Jotul 550 is running at right around 500. The temps are about 68 in the room it's in, 65 upstairs and 62 in the far reaches. of my 2800 sq ft. Medium load of locust and I can't raise the temp. I'm fairly impressed considering it's a flush faced insert. Keeping the oil burner off until the am then let the heat come on and even things out. All in all it's good but if it gets any colder I can't keep up. When it was 20 earlier I could raise the temp in the house, now I can just maintain. I'm lucky the heat distributes pretty well naturally in my house or I'd probably bust a pipe, it's cold enough.