My gut instict: Unless the heat pump is massivly oversized and needs to run below the minimum power threshold than you would be fine. Each case is of course different but I would not think the difference between a 7kw HP and say an 11kW HP would matter.
Using the variable speed, weather compensation and smart controls should do the job.
A buffer tank could help too to stop short cycling (<10 minute cycle.)
Years late with the input, I now realise!
I am a bit unsure about this, as I thought I listened to a few things about heat pumps where the efficiency is significantly impacted when you have either undersized or oversized the heat pump. We all should reach somewhere around the 400% mark with a new heat pump and hence it would be good to have the final insulation, windows, etc up before you get the heat pump.
However strategising those retrofit is so difficult and all depends if your boiler lasts long enough so you can wait until you have the insulation and windows installed … and then still have the budget for a heat pump.
Why is retrofitting the right way round so difficult?!
Please continue heat pump discussions at
This thread can then concentrate on EPC criteria.
Yeah which is silly when we already have toold which measure energy use such as PHPP.
They should just say. PHPP analysis can also provide EPC’s. Although it would ruin the credability of SAP