If the lowest my winter temps got was 40, Id not have to have a wood stove!! 40's all winter would be balmy! As Ive said with my NC Defiant. Im happy with it thus far except that damper lever issue which is now resolved, but Im reserving my final judgement until after we've had "real" winter. As far as I can tell, mine is working ok. Ive used the tips Elk has given. But, then again, I wouldnt really know if it WASNT working ok. Once I engage, I hear the rumble and my top temps seem to hover btw 5-600 or so until it gets burned down. Thats with the air control fully open.