Heat pumps are tested to nominal outputs, some manufacturers tell installers to design to PEAK outputs and this video explains why that is a bad mistake not only in design practice but it also goes against MCS regulations.
Oh and your house likely won’t reach design temperatures and will leave you cold in the winter. Fun times.
What happens if my designer choses peak kw outputs for my heat pump?
You might get lucky. It depends how close to the limit of the heat pump, your property heat loss is.
A likely scenario, and one we have seen many many times now is that your house will not get to your target room temperature of 21c, for example.
Your heat pump will be working at or near maximum capacity for much of the time, shortening the life of the heat pump.
Your installer may come back and tell you they are installing back up heater elements to make up the shortfall. RED FLAG.
Back up heater elements will indeed take up the shortfall but will also cost you more to run. 2kw of heat from a heat pump might only require 400-500w of electricity due to the refrigerant cycle. A back up heater element is direct electric so 2kw of heat will cost you a hair over 2kw of electricity: four times more…and you will be paying for that.
Not to mention again, this too also goes against MCS regulations.
Choose your designer wisely.