I'm totally skeptical about that claim. Granted that there is some loss during startup and cooldown, there's no way that storage makes that much difference. If anything, our wood consumption increased slightly. I attribute that to keeping the house and hot water warmer with the storage, but there's no way that there's a 45% difference. Hard numbers: 3.2 cords November 21 through March 15 without storage. 4.5 cords November 1 through April 15 with storage. I haven't counted up degree days and compensated for hot water load, but perhaps there's a small efficiency boost with teh storage. I do know that comfort and convenience improved dramatically.