Renovation of heating system for existing property - condensing boiler/air-water heat pump/DHW heat pump

and the photovoltaic system (the only investment that particularly pays off in connection with a heat pump) later? No, the interest rates are still low, going for it right away with the new roof (good photovoltaic = roof fully covered) if it is financially manageable in any way.

Would definitely only be at the expense of the other renovation costs/works. Whether it is even financially feasible, I have to see...

Photovoltaics must be considered completely independently. It is a (very sensible) investment. One that is worthwhile even if financed (KfW). However, it has nothing to do with the rest. The little it can contribute to heating electricity is not decisive for the war.

There are no alternatives to heat pumps (even if some think so). Your task now is to make it as comfortable as possible for the heat pump and yourself.

So you mean, if without photovoltaic, it should definitely be calculated. According to your experience, it would probably come out that it is economically justifiable. Sounds good to me. How much would such a calculation cost? That can also be done by a decent energy consultant, right?

It must also be calculated with photovoltaic. The room-by-room heating load calculation including underfloor heating design should NOT be done by the energy consultant, but by the planning office. It might cost around 150-200€. For example, Büro Heckmann.

Thank you for your answers. It is now up to us to make a decision. Basically, you hear the same from many: heat pump, ideally combined with photovoltaics.

But I have one more question: based on the room-specific heating load calculation, can the heating engineer select and set the appropriate heat pump as well as underfloor heating and/or low-temperature radiators accordingly? The energy consultant could then check it again (based on the offer or similar) and handle the applications, for example with [BAFA]?

Theoretically yes. Practically, most heating engineers and energy consultants are bad. But basically you are right... Self-monitoring is advisable. In the end, these are numbers that can be added up.

You can submit the Bafa applications yourself. I wouldn't pay anyone for that.

Addendum: If you mix radiators and underfloor heating, you should make sure that the radiators are calculated so that they get the same supply temperature as the underfloor heating. You do NOT want to use a mixer.
And: The maximum heating load determines the size of the heat pump. No surcharges for a good feeling or domestic hot water preparation.

I have one more question: based on the room-by-room heating load calculation, can the heating engineer select and configure the appropriate heat pump as well as underfloor heating and/or low-temperature radiators accordingly? The energy consultant could then check it again (based on the offer or similar) and handle the applications, for example with the BAFA?

You also have the underfloor heating planned by a professional. Because they then design it to achieve the lowest possible flow temperature. The heating engineer says: we have always done it this way. And the energy consultant is an advisor and not necessarily a technically skilled person.