figure a upgrade to 200 amps just for water heating, plus the service
for everything else.
will cost big bucks probably several thousand.
now crack a valve for say washing your hands might get cold water,
because the minimum flow wouldnt be met.
now if you live in a area that freezes, nice hot water may be cool when
the incoming water is cold.
figure you will save money? the energy saved by no standby losses only
matters in summer in cold weather it just helps heat your home.
the tankless cost is so high any savings will take longer than the
tanks about 10 years expected life.
if you want more hot water just buy a regular tank of bigger capacity.
we should make a FAQ on this as it comes up all the time.........