If you have a solar PV system, you should either install a power diverter to produce hot water, so that you do not need to run your heat pump at all. Alternatively run your heat pump to produce hot water when your solar PV is giving maximum generation. Whilst this will not actually change the recorded COP value, it will reduce your actual energy consumption, and is more environmentally friendly.

Hi all

I wondered what sort of DHW COP others are getting from their Ecodan's? We have the combined system with the pre-plumbed cylinder and over the summer have had the room heating switched off so only the DHW is working. In July and August we have only been getting a COP of c. 1.9 heating the water to 45-47 degrees. Does this seem right? Feels low to me?

Thx

About 2.1-2.2 for me. 14kWh Ecodan and external HW tank.

I think it depends how you have it set up and your HW usage.  If you heat your HW once a day at the warmest time of day and use a lot of HW the COP will be better because the ASHP will have a chance to get going and run for a while in steady state.  If it's constantly topping up every time you wash your hands then it's going to be doing a lot of cold starts, which is inefficient. At least when you do this in the winter, the flow is already 40C or whatever, in the summer the flow starts at room temp. The ASHP uses a lot of power from a cold start, more when the flow is colder.  

The other thing to be aware of is that even though your tank is set at 45C, the flow water will be hotter than this otherwise it would take too long to heat the tank.  How much more and for how long depends on whether you use Eco or Normal settings.

Thx