celticsgreen said:
Anecdotally I am reading that some people feel that super-premium pellets will do a better job on a cost per btu basis...however objectively there is no evidence....especially since the cost differential is not linear.
Getting objective evidence is difficult, since that requires controlling a slew of variables. You'd need to have a number of different stove designs, arranged in an array of standardized buildings in the same climate, tended by people with about the same cleaning skills. Then you'd have to run studies over a long period, with different brands of pellets, while analyzing the pellets to be sure that each batch of a brand is consistent.
What's well-known for wood stoves is that any buildup on the interior will cut heat output. So what burns cleaner will result in the stove putting out more heat, if the cleaning interval remains the same. It's not the amount of ash you've got on the floor of the stove. It's the buildup of ash and whatever on the front and sides and top - especially the heat exchange tubs on a pellet stove. The BTU rating on the bag's contents doesn't tell you that. Neither does the ash content, strictly speaking, since some pellets proportionally leave more of that on the floor of the stove, while others dirty up the stove where it matters. So when folks report feeling a lot more heat from their stoves with good pellets, that's what's going on. It's not just how clean they burn, but whether it's the right kind of clean.