Someone commented on the high cost of the instant hot water heaters...
Well about five years ago I made one out of parts that can be pretty
easily bought for around fifty dollars and it is still going strong...
Essentially it is made out of 1 inch galvanized pipe and T-fittings..
The T fittings allow you to screw in the screw-in type heating
elements into the heater... On mine I put in a flow switch (that I
got from a surplus place but that could be bought from a plumbing
supplier) I wired that to a 240 volt contactor large enough to handle
the flow of electricity... (I got mine out of a junked large air
compressor)... and I screwed in two heating elements in series into
the one inch pipe... All sort of hard to explain... but you get the
picture I hope.. It doesn't take up much room and remarkably it is
still working well years later.. I had commercial bought ones before
and got tired of replacing expensive little parts in them (like their
heating elements that would burn up if some air got in the line) or
their electronics which seemed to be damaged by power surges... etc..
This thing I have now just won't quit and when it does I can just get
the parts easily and cheaply... I don't have the luxury of a really
steaming shower (especially in the winter when the incoming water is
colder) but my power bills for a 3 person household are under
$25/month so I can live with it..