If you are using electric water heating, now I wouldn't bother. There is not
really any gain in economy.
Your lights may dim and you could overload your electric service, depending
on how modern your wiring / fuse panel is.
I doubt you will have enough hot water supply to supply a shower and a dish
washer at the same time.
My rinnai gas unit runs 185,000 BTU and it can be "just barely enough"
Learn the BTU math and get educated so they can't sell you the "infinite
supply of hot water" BS. If your water comes form the ground at 45F your BTU
cannot produce as much volume due to a limited BTU rating. Do the math.
There is also (in a gas unit moreso) a delay in reecognizing water demand so
if you trun the tap on and off repeatedly you may never get hot water. This
inputs a cold water shot ("sandwich") in your pipes if you did this in the
home depot and lowes sells these, models requiring either 2 x 40 amp or 3 x
breakers, depending on power
has anyone installed these and what are your observations / recommendations