Not sure if there has been much documentation on this but I thought I'd share it. I have a P68 which has a reasonably good sized ash bin. Emptied it for the first time today. I've burned 35 bags so far - the bin was full to brim. Totalled 6 lbs (after subtracting the weight of the empty bin) Thought I'd keep track for each brand of pellets I use. Not sure if 6 lbs is a lot since this is my firt time. Currently I am using a Canadian brand "Granules" (So much for buying USA) I have no reason to complain but I have nothing to compare it to.