Efficiency of air source heat pump water cylinders

Matt0029

Gas Engineer
Does anyone know the efficiency levels of the unvented hot water cylinders with a heat pump on top with vents to get the air in to it. I think I'm correct in saying a normal direct unvented cylinder will be 1kw of electric to 1kw of heat
 
I have an ASHP heating a hot water cylinder and providing UFH. HW is set to 50 deg C with a Legionnaires cycle once a week.
Mine is not the integrated tower system of which you speak, but I don't see why the performance should be much different.

Around this time of year I get a CoP of 2 for HW and a CoP of around 3 upwards for the heating - better in warmer weather.
If the temperature drops well below freezing, the performance falls off.

As long as it's not really cold weather, it means for each 1kW of electricity used I get 2kW worth of hot water.
That's not as good as some manufacturers claim, but looking around on forums it seems reasonably typical, though some get better for heating
 
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