ASHP install questions

michaels

I would just say that for a poorly insulated home, not only will you need to have a correctly sized heat pump but you will also need larger emitters - which in the extreme might be infeasibly large - as without these you would need a high flow temperature which will be less efficient than a lower flow temperature. With a traditional heat source you do not get the same loss in efficiency from running higher temps with smaller emitters (up to the condensing temp limit)

Tallmark

Ultimately all of this speaks to having a reputable heat pump installer who carries out a detailed heat loss survey of the property and then designs a system that’s right for your house. I’d highly recommend using the Visit-a-heat-pump web site to see local installations and help shortlist installers.

matelodave

TBH even running a heat pump at a COP of 3 or even less is more efficient than a gas or oil boiler.

The problem isn't really loss of efficiency its the fact that leccy is four times the price of oil or gas. If there was some degree of parity then even a COP of 1 would be more efficient than gas or oil.

NedS

https://forums.moneysavingexpert.com/discussion/comment/81920214#Comment_81920214

Of course you are correct, but generally people are not (ultimately) interested in efficiency - they are interested in cost.

The two things that directly affect the overall cost are the unit cost of electricity and the efficiency. Both need to be considered when trying to bring down the overall cost of running a heat pump as both will have an affect.