Which heating is recommended for KfW 55?

A Rotex HPSU Compact with an integrated 500L hygiene buffer tank and an annual performance factor of about 3.9 is available for 6,900 euros including shipping. Commissioning is available for 700 euros.

For 22,000 euros, they should already gild the thing for you.

Under normal circumstances, an air-to-water heat pump is priced the same or cheaper than gas+solar. But your [GÜ] apparently wants to make a good profit here, so it probably isn’t worth it for you.

Advantage of an air-to-water heat pump with the right model (like the Rotex): it can cool.

Air-water heat pumps et. al. have such a good annual performance factor only because, according to the advisor, the electricity can theoretically be generated from renewable energies. He believes that in the coming years the government will backtrack on this. Industry associations are already demanding such changes or modifications. I have not verified these statements.

That is complete nonsense. Either you misquoted or the energy advisor has no idea.

To determine the annual performance factor, you divide the heat generated in kWh by the electricity consumed for heat generation (also in kWh) over one year.

These are two figures that can both be determined at home, so how should the German or individual electricity mix have any influence on the annual performance factor?

Perhaps changes in the calculation of primary energy demand are meant, but these have nothing to do with real consumption (and I doubt that anyone can just change the formula for calculation...). From my understanding, rather long-term political decisions on how our electricity should be generated should have an influence here, e.g. which power plants will be needed in the future and only through that the primary energy factor for electricity changes. Depending on the development of the power plant fleet, the factor improves or worsens, for example compared to gas. Currently, the primary energy factor for electricity is 1.8 and thus worse than for gas (1.1). Before 01.04.2016 the factor was even 2.4.

The factor influences whether the requirements of the Energy Saving Ordinance can be met or not.

Hm yes, I could indeed have confused the factor for primary energy with the annual performance factor. Thank you for the hint.

Salvatorische Klausel: the rest remains as claimed/represented by me.

Severability clause: the rest remains as claimed/stated by me.

Which suggests that you do not yet have an objective overview of the different heating technologies.

It would be very surprising if a house with an air-to-water heat pump could not be built cost-neutral compared to a house with a gas condensing boiler.

Most recent posts in this forum contradict this.

Most current posts in this forum say otherwise.

Really?
I rather got the impression that construction contractors have their preferred solution and make deviations from it exorbitantly expensive. Just upselling. Costs more money because the preferred solution was not agreed upon beforehand, was bought in bulk, and/or the deviation from the standard involves additional effort.

That both system types are priced similarly by a heating engineer is a completely different matter.

Yes, really. You yourself explained the deviation, the general contractor / house builder has a standard from which he only wants to deviate for an additional charge.

But that does not mean that there are no providers who either sell air-to-water heat pumps as the standard nowadays (Bauexperte, for example, if I remember correctly) or who look at each house individually and decide on the best heat generator; it definitely will not result in gas condensing boiler + x = air-to-water heat pump.