Hyco Aquila Instantaneous Inline Water Heater with 9600-Watt Power Output,

we have a large accumulator tank that is heated by a wood burner which usually supplies good hot water however sometimes based on incoming temps and also whether we have had the burner on it can be slightly cold. Plus the water in the pipe is usually cold. This heater tops up the water to the exact temp required meaning 50 deg water within 2 cup fulls and then it backs off as the water coming through gets warmer. It will shut off if the water in the accumulator is warm enough. We have it set on 50 deg. It is feeding a thermostatic shower and 2 mixer taps. You have to be a little careful with flow rates but so far the power control on this seems more than capable of handling the varying demand and keeping the shower and taps running at the right temp and the flow rate to the bath is good. Even when the incoming water is cold the flow rate is adequate for a reasonable shower although if it was the only heat it may be slightly undersized.

Installation instructions contradictory (says pipe connections at top in one place, in bottom another place), but simple enough what to do. Doesn't heat water as hot as previous heater - only quite warm, rather than hot.