Wood-burning efficiency is affected by an enormous load of variables. Besides what stove or insert you’ve got—what is the length of flue above it? Is the flue triple-wall insulated going up through the inside of the house, or brick and clay tile directly exposed to the north wind? Is the draft wide open for a clean burn, or closed down somewhat to extend burn time? Is the wood plenty dry, or still holding some moisture? Large diameter chunks vs. small splits. Hardwood vs. less dense. Outside temperature of 44 degrees or 18 below zero. And so on and so on.
I’ve burned wood in many stoves and in several houses over the years, and every stove and situation is different.
Right now my main floor heat comes from a Hampton HI300 insert, with the blower pushing the heat into the room. Down in the basement I’ve got a Hearthstone Homestead freestanding soapstone stove. The same wood burns different in each one. The downstairs stove will burn down to nothing—no coals, just pure ash—if I don’t stoke it in time. The insert will hold coals a lot longer. Same wood in both.
Like someone said above, in real cold temps if you keep pushing wood into the insert before it has time to fully burn the coals they build up and become a nuisance. To reduce a giant bed of coals I rake them to the front and crack the door to get the venturi effect.
But all in all I like both my units. The glass doors alone are worth the price of admission. At beer time in the evening—Jeez, it comes early this time of year—I like no other light in the room but the fire. It’s pretty near hypnotic, way better than TV for my viewing pleasure.