Air source heat pumps

[hiddenmnetter]

Does anyone know much about them? In this protracted heat I’m thinking about getting A/C installed but was leary about the running costs. Apparently new designs mean they run efficient to a factor of 4. Does anyone have any experience of this? Is this a consistent coefficient or is it wildly variable? The salesman told me a 7.5kwh unit can run off a 13A fused spur (the actual draw is around 2kw).

I’m tempted to be able to cool and heat 3 rooms rapidly for less than 20p/hour, but I don’t want to be in the situation that I’ve spent £1,800 to purchase and install a unit that won’t do the job because it’s only designed to draw a small load.

The are two sides to them, one is heat pump where it uses electricity to import heat from outside, this can be up to 4 to 1 of power used to heat put inside. That would make it slightly cheaper to run them a gas boiler. But it varies depending on the outside temperature.
Then there's the air conditioning side which doesn't get the extra efficiency boost because the wasted heat would go outside.
A ground source heat pump is more efficient because the ground has a higher heat capacity so you can take more out in winter.
Hope that's useful

I get that about the GSHP but the salesman (and all the reading material I could find) says that there is a COP for cooling as well - effectively you are turning your house into a fridge, and that it can supposedly get very near equal COPs. Or is that not the case at all? And if it isn’t the case at all, how or why would a 2kw condesor unit be able to supply up to 7.5kw of cooling? Or am I totally lost here?

I’m moving into a new build with one in just over a week. Happy to report back once it is in use! We have no gas here (rural). It’s a super insulated but cottage style house.

Yes the efficiency of heat transfer is not a theoretical limit like an electric fire, it's just down to how the system is designed. But much like central heating you need to calculate the demand correctly based on the design temperature and construction and aspect of the house.

We have air source heat pumps. Two for the house and one for the pool. Ours heat underfloor heating and conventional radiators. We have a highly insulated house. We also have no gas. Oil deliveries were very tricky due to narrow access.

GSHPs need a huge amount of land and the garden will be dug up big time. We have a super garden and it was too much work to reinstate it. Our ASHPs have been fine but water is heated to a lower temperature. We don’t mind this. I cannot see how you can run air conditioning unless you have a hot air/cold air system, not radiators or underfloor. However, when it’s hot, stand in front of the pumps when they are on: nice cold blast of air!

Sorry if it wasn’t clear from the OP:

I want this system for the purposes of cooling. It will be air-to-air rather than air-to-water. My question is whether or not the COP that applies to the heating and cooling (approx 4) is reliable and what factors vary it?

Additionally will the 2kw system I am looking to install have the capacity to overcome very hot weather if the COP isn’t great?

I will probably also use it for heating in the depths of winter to make the room toasty before waking up, but otherwise it’s really about A/C for south facing rooms that are around 28 degrees at night.