Thats what it says on the brochure in low burn mode. Got to thinking about that number. Yes quite impressive. But how many of you have really thought about how much your stove actually uses. I know I don't burn 80lbs in that amount of time on high burn. Difference is I don't load it in all at once. Since I'm sure thats only possible on the very best of wood perfectly dry I can only imagine or compare to how far I can go on 80lbs of Ecobricks. For me 4 bricks (half pack) (10lbs) will last 10hrs. So 2 full packs doing the math would equal 40lbs/40hrs. Now add in a few splits, and I do mean a few, that are typically maple for me or very dry Elm that is feather light there is no way I would get to the 80lb number. So when you really get down to it, its the ability to burn slow enough to load it in all at once. But in reality probably anyone can have that same performance at little bit at a time. Last night I loaded in 4 bricks and 4 splits. 10hrs later stove was 300 degrees. Starting temp was 750. I would be curious to know if 80lbs of the bricks were loaded in at one time how far the King could go. I have yet to even load in a whole pack at once (would fell like I'm wasting them). Most I've done is half pack. I started out putting in 2, then 3, then 4 for over niter. I mostly use them as energy pills for existing firewood.