Can I get some discussion about the amount of wood burned by a Rocket Stove over a wood stove of around the same output? Looking at the numbers I note that a rocket stove in a larger space doesn't seem to be even close to as efficient as a good wood stove.
Hmm, what numbers are you looking at? The general experience reported from people who have switched from using a woodstove to a rocket mass heater has been a dramatic decrease in wood consumption, often less than a quarter of the former consumption.
To me the two are not all that comparable, especially on a BTU basis. Really what is important is "how warm do I feel factor". A rocket mass heater is superior because it takes the 26 million btu's in a cord of wood and makes you feel 26 million btu's of that wood. With a wood stove you might feel 13 million btu's because the rest is going up the chimney.
But it takes considerable time to build a rocket mass heater, they are fussing on their design details, they take up space in a home, and are prone to weather variations. In contrast a wood stove is ready made, already engineered out, and works by sheer volume of wood being consumed within it. Done right though, they do take up space in a home...maybe not as much as a rocket mass heater, but it is a considerable loss to living space.
The real question is, how much wood do you have available?
For me, I live in the most heavily forested state in the nation (Maine) and have hundreds of acres of forest. It took me two days to cut the 5 cords of firewood I need for my home this winter. Since I used a pot bellied stove, I use waste wood from my logging operations...limbs, brush and saplings, so my wood is tiny in size. I also have the forestry equipment to gather volumes quickly. Some people do not have this. So for them the better alternative is a rocket mass heater that uses less wood, and uses smaller sized wood that there area has. I have NO ISSUES with that at all. Some people fall in between these two extremes and their decision making might be harder.
So too will time and skill set. I am confident I could build a rocket mass heater, but again this is a heavily forested, cold state so used wood stoves abound. I just had one given to me, and installed it (myself) for $115. That is probably comparable to a self-built rocket mass heater. But again, it depends on the homeowner. If I was to sum it up i would say that few people would ever regret building a rocket mass heater, but for many of us, a "wood stove is efficient enough" keeps us from building them.
Well in our studio/greenhouse we went from 12-15 cords And an always cold perimeter in the room, to less than 5 cords and nice even temps around the whole room. We love our RMH!!! You mention heating a large space ... like cathedral ceilings and ranch house spread out?? A RMH will not do as well in those locations. Bottom line, if you have a large spread out house in true cold country your rmh may need help keeping the far reaches warm... but hey even a standard wood stove lets those back rooms go cold at 5 am. The smaller volume of wood burned makes it a winner in my book plus for those of you are concerned about the leadership of our society ...when you don't have any gasoline being delivered it makes it hard to cut 10 cords of wood for that big blaze king in your living room.... My RMH can burn dead branches and pine cones AND it only needs to burn a few hours a day !