Solar module efficiency is what, about 20% at best? Thermal is more like 60%. This means less roof area needed on a house that doesn’t have a lot of solar exposure.

So anything above a CoP of 3 and you need less area. That’s pretty doable these days. Maybe read up on how heat pumps work first before making assertions.

Also you can totally store hot water from a heat pump.

The main disadvantage is cost and complexity.