Hard to say, I had one load this weekend that would not build cat temps like all of the other loads. Had to play opening the air to get it to finally take off. Every other load cat would rise nicely, I'd close the air down the cat would drop then rise again and cruise nicely. Same wood well seasoned mixed with a bunch of locust in it. I've kept the stove hot the last few days as temps dropped into the 20's at night, high 30's low 40's during the day.