stee6043
Minister of Fire
Don't get me wrong, I agree with your thoughts that the unit's claims seem a little fishy, but am not clear on the quick math. Are you saying that the house only has a heat load of 30 kbtu. I would expect the unit (with a 100 # load of white oak) to be capable of providing much more than a 30 kbtu output. If the house/user only had a demand that size, it certainly wouldn't require a full load of premium fuel to accommodate.
I was just basing that on the Kuma website. The claims are not abundantly clear but there is a page that says "30k-40k btu/hr output" and immediately below it seems to suggest it can go "up to 10 hours - heats up to 3500 square feet" in that scenario. If the output is 30k over a period of 10 hours and you had a mostly full load of theoretically perfect white oak you'd be rocking sub 50% efficiency. Of course, you're going to need to forget you saw immediately above this that the unit will burn happily on 28% moisture content wood as well.
Again, this is not exclusive to Kuma. I think most burner/boiler MFG's are marketing whizbangs that are doing everything they can to baffle the wood burner buying public with lots of numbers. 99% combustion efficiency is the most awesome example of marketing awesomeness. I think even my EKO claims something north of 95% "efficiency" even though all of us EKO owners know we're running in the 80's with storage and properly tuned air setups. My point is only that buyers should do their own math before investing their hard earned greenbacks in any heating technology.