I used to think they wouldn’t work with water filled rads and that they needed a really well insulated house but apparently neither is true. Whether they work with water filled rads is dependent on the bore of the pipework.
I always understood that if they were to have any usefulness your house needs to be really well insulated, but maybe that’s changed.
I think all new builds are meant to have them going forwards so we’ll all have to learn about them at some point, presumably the tech will continue to get better though so not sure when the point will come when it’s worthwhile to make the switch.
What appeals to you about having one? In general, if you only want to save money there are probably better options, as the return on investment period is at least 10 years. If you want to do your bit for the planet and also potentially save a bit long term, they are great.
Ultimately we’ll all have them, or similar technology. I’m planning to get one installed as part of my house renovation. Can answer more detailed questions if you know what you want.