Using PV energy to run a heat pump?

Reed_Richards

Underfloor heating works well with a heat pump because it tends to require a lower water temperature than radiators.  The downside is that it responds very slowly so you have to keep the heat source on for long periods.  A mixture of underfloor heating and radiators may not save you anything at all compared to all radiators because you need hotter water for the radiators.  It could work but the heat pump needs to know to throttle back on its output when there is no demand from the radiators.  This could be really tricky to accomplish if the UFH was being introduced bit by bit.

ABrass

I'd look at when you think you can get the work done and sequencing.

If you're doing this over a period of years then focusing on getting the house shell insulated and a new heating source installed is the top of the list. If a heat pump is going to push back double/triple glazing by a year and cost more, then it might not be worth it.

Sorting the shell will leave the radiators significantly overpowered, which would work well with a heat pump and in the meantime boost your green credentials by reducing gas usage and saving money.

Doing solar would help reduce bills but it shouldn't be allowed to delay getting the roof insulated.

If you can insulate the house and get a heat pump at the same time then it's worth considering, but I suspect you'd be better off financially and comfort wise delaying the heat pump.