"IMM" wrote in message
...

There are some Americans who have these
installed and reported figures on them. The average
temp rise is 17C. In effect it makes your cylinder bigger too.
When showering they are effective because you are
heating the incoming cold water with waste water simultaneously.

So if you have a combi that gives 11 litres/min @:35C temp rise, then having
one of these pre-heating the mains water to the combi will give and extra
50% temperature rise. In effect making that 11 l/min to approx 17 litres/min