[sneuman]

I can only speak of on-demand water heaters in general. They are common in households in Asia. Work wonderfully - unlimited hot water instantly; they are also very efficient, heating only when needed, not wasting gas/electricity to keep a pot boiling (or near boiling). I have been living in Asia for several years now and cannot understand why this idea hasn''t caught on in the states. Just makes too much sense. But, like many other things, the USA is WAY behind vis-a-vis the rest of the world.