Well I got home tonight and the house was 61 degrees. I built a fire in the insert and now two and a half hours later the house is 66. I'm measuring the temperature with the thermostat from my furnace which is in the hallway, so it's pretty good indication of the house overall and not just the room the insert is in. That's a temperature increase of 2 degrees and hour. That's awesome considering it was 27 outside when I lit the fire and it's 24 now. I ran it a bit harder than I have previously but still no way near over fire temperatures.