Just read
this article published by the BBC quoting a guy at Octopus Energy with regard to recent improvements in heat pump technology who, describes installation of their Cosy 6 air source heat pumps as "little fuss" and as simple as "Combi boiler out, heat pump in". Anyone have, or come across, a heat pump that can really replace a combi boiler and generate instant hot water direct from the cold mains?
The technology for air source has improved, however basic physics has not.
To run a heat pump at similar or lower cost than a gas boiler in the U.K you need to design a heating system that will work at low temperatures. i.e. when its -3 outside I only need my radiators to be 40 degrees in order to keep my house at 20 degrees. So this would suit a heat pump nicely for running costs.
If I needed to run my radiators at 70 degrees to keep warm which is more like traditional gas heating systems then it would cost an absolute fortune to run a heat pump at those temperatures. (still cheaper than running electric heating, but much dearer than gas)
Many houses, especially older properties have radiators that are massively oversized, so its often the case that they could actually be suitable for heat pump temperatures, however the pipework needs to be assessed as they need more water flowing through them than with gas boiler systems.
Again, some properties it's not really that big an upheaval, some its pulling the lot out and starting again.
And when the person who sells you electricity is selling you electric heating I panic. Are they fitting a heat pump to a very inefficient system and being offered a cheaper rate of electricity to mitigate the running costs?
As far as a combi/heat pump, I'm sure someone somewhere is working on it, however in reality it would be incredibly difficult to do, and would not save any space as already suggested due to the size of heat pump required to run it, and I'd be certain if they did make one it would cost a lot to run.