I was, money in hand, ready to go tank-less, but am thinking better of
it. I think the savings projected depend on an ideal situation. I lack
that. If you have a situation where the runs to the taps or appliances
that use the hot water are short, it might be a savings. If you are
gone and the house is empty more than occupied, you might see some
savings. The consensus here seems to be that it would be worn out
before the pay off ever came and in the meantime you would have a noisy
expensive unit that few people know how to repair, and no reserve hot
water during a power outage.
My plan now is to put in recirculation loops on the units I have and
get instant hot water at the taps. That plan might use a tad more
energy to heat the water, but should eliminate a lot of wasted water,
which in my case has to be pumped.