I've worked with air to water heat pumps on various projects over the last 15-20 years and they do work but they have to be correctly designed and that means the entire system.
There is a lot of confusion about what these are, how they work and the different types and it was mentioned above about a unit that provides heating and cooling, although that uses the same basic principals that is a different system which doesn't use water as a heat transmission medium.
If using an air to water heat pump to heat a house you need to consider the following:
- The temperature that they produce is lower than a gas boiler, therefore the amount of heat you get out of the radiators reduces for a given size. You therefore need bigger radiators.
- As mentioned above they are less efficent as the outside temperature drops and therefore they need to be sized to cope with this.
A lot of the problems that I have seen are caused by designers/manufacturers installing the wrong sized unit on the basis that it works when its 10oC outside but when it drops to 0oC or below it then has an electric immersion heater that comes in to boost it which increases running costs. This is due in part to manufacturers all trying to make their units look comparable or better than their piers so they make misleading claims that inexperienced designers/installers don't pick up on.
They can be made to work successfully but insulation is important and its very difficult and expensive to insulate a lot of the older housing stock (anything with solid walls particuarlly).
The whole air to water heat pumps are rubbish arguement is not correct, they are reliable proven technology that tends to be badly designed and installed leading to the reported problems.
With the rising cost of gas and the increase in production of low carbon/renewable electricity the switch to a heat pump will soon make a lot more financial sense, however,at the momement i'm not rushing out to change my three year old boiler (came with the house when I bought it) but when the times come (probably sooner rather than later as its a Baxi boiler and its already failed once requiring replacement of most of its components) I will happily install a heat pump for my house.
Edited by Homersimpson, 27 October 2021 - 08:17 PM.