According to News :

"Phil Sherrod" wrote in message
...

What I disagree with is the assertion made by others that they save
significant
money over a tank heater.

Condensing versions do. See:
http://www.ravenheat.co.uk/productsCSI85.htm

You've switched to an apples-versus-oranges comparison.

There are condensing versions of tank type water heaters too.

What Phil has done has shown that given _equivalent_ technology
the MOST that a tankless heater can possibly save you is about
$4/month (assuming electric in both cases) - the cost of running
an electric tank type heater without any demand for a month. Since
the technologies are equivalent, the cost of heating water you
actually _use_ have be the same[1].

The choice between tankless and tank-type should normally be made
on other factors - ie: speed of delivery ("instant"), physical
size, location, etc.

Here's another factor to consider:

Unless you're using gas, tankless heaters require much larger ampacity
circuits, which can be a problem w.r.t. peak loading.

Note especially: we have a new provincial initiative to use timers on
high load items to shift them off-peak, coupled with electric meters which
give you lower rates for off-peak usage.

It occured to me that it might be a good idea to put our HWT
on a timer so that it only runs at _night_, and operate off stored
heat during the day.

In a regimen like that, it may cost _significantly_ less to run a
tank-type heater, because the tankless puts most of its power
consumption during peak (higher cost) times of day.

[1] There's one significant difference between tank-type and tankless
which _will_ be somewhat of a factor in efficiency given the same
heating technology - the length of the plumbing. Since tankless
are smaller and tend to be put much closer to the point-of-use,
energy consumption to heat up the outlet pipes will be _much_ less
with tankless. If your pipes are uninsulated, this could be quite a bit
of money.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.