From when is a heat pump worthwhile in an old building?

[*]Solid construction from 1970
[*]Basement: fully basemented, basement height 201cm, exterior insulating paint, 11.5 cm calcium silicate solid brick 1.8/250
[*]Ground floor/attic: 11.5 cm calcium silicate solid brick 1.8/250, 2cm styrofoam, 17cm calcium silicate 1.4/150
[*]Roof: collar beam roof with concrete tiles, insulation also present

Of course, we would install underfloor heating here. But does a heat pump even make sense with the above-mentioned data? Or would it be better to opt for a gas heating system here?

What have you had so far for heat demand / consumption? What other measures do you have planned? What does the engineering office say about the room-specific heat load calculation or heating system design?

I can tell you that this winter in my (still) uninsulated mid-60s old building with a new underfloor heating system and mostly new windows + basement ceiling insulation, I have not gone beyond 30 degrees supply temperature for 21.2-22 degrees indoor temperature. The consumption cost is about half of the previous oil consumption (which in recent weeks has shifted even more massively in favor of the heat pump).

In general, it is therefore possible to install a heat pump, right?

The search for a gas provider should already provide the answer. ;-)

In general, any house can be operated with a heat pump. It's just a matter of how much effort is required. Underfloor heating is already a great prerequisite. An insulated roof as well. Then make sure that the wind doesn’t blow in anywhere and insulate the basement from underneath as a DIY project. Then, with the help of various forums, properly size the heat pump, leave out the buffer, and you will heat cheaply and environmentally friendly.

Actually, it would be helpful if you could get some data from the previous owner, such as oil consumption and room temperatures. Then you can make initial rough estimates of how well or poorly the house is insulated.