Four years ago we bought a norwegian Jotul F 3 CB. Efficiency is quite high
at 70 per cent. It is the most sold stove in N America. For just a 23x19"
stove, it cranks out 42,000 btu and will easily heat 1300 sq ft of space. We
love it, as we live in foggy coastal area, and use it sporadically year
round. However, for us, it occasionally substitutes for central gas heating,
does not replace it fully.
Try this question on alt.energy.homepower - lots of expertise there. They
can give you the metrics on wood use rates, alternate fuel comparison, etc,
but as the prior poster says, depends very much on your area fuel prices,
weather, local restrictions, and source and cost of wood.

wrote in message
oups.com...
Gas costs a tremendous amount right now. I guess I don't know how long
a cord of wood will last.