Replace gas with heat pump

Even if the solar system and the buffer tank remain (which would be nonsense) and the installation spacing of the underfloor heating is reduced, an additional cost of €12,000 is not obviously justifiable. It seems like the contractor just wants your best... Save yourselves the extra cost and rather invest more money in an expert who supervises the contractor's work...

We faced a choice: gas or air-to-water heat pump. Ultimately, we decided on gas and do not regret it. 160sqm KfW55 without a basement including solar-supported hot water and controlled residential ventilation costs us about 40€ per month (including hot water). How low do the costs have to be before you recoup a significant extra price for an air-to-water heat pump?

How low do the costs have to be before you make a significant premium on an air-to-water heat pump?

So we have 157 m² Kfw70 with an air-to-water heat pump and the electricity provider has set a payment on account (!) of 80 euros/month. I don’t know yet what the final amount will be. But on May 10th, the heating is still running. Gas would have cost us an extra charge during construction, and at that point I was stingy.

On the other hand, the ratio of electricity and gas prices can change again. Oil, and therefore gas, is as cheap as it hasn't been in a long time. Electricity is expensive because of taxes/levies.

Operating costs could develop pari. But how long will the pump last without expensive repairs? The gas boiler runs almost maintenance-free for about 15 years, Karsten

The operating costs could develop evenly. But how long will the pump last without expensive repairs? The gas boiler runs almost maintenance-free for around 15 years, Karsten

Heat pumps are initially low-maintenance to maintenance-free and also do not require a chimney sweep.
Durability is a crystal ball. When replacement is due, the gas boiler is cheaper in terms of investment (if still allowed then, see oil).
Consumption costs are written in the stars. Gas prices can regularly double from one year to the next; we are currently experiencing a price low. 40€ sounds nice, but it can also easily become 80 or 100. Electricity prices are rather stable or gradually rising, as they are significantly less influenced by speculation and international political mood; moreover, the energy source is interchangeable up to self-generation.
But of course, this is based on the past; the future is unknown.

If gas, then so that it can be replaced by the next investment cycle. Who knows if the burners will still be allowed forever; the Energy Saving Ordinance already penalizes this system. For heat pumps, I would immediately think of ground source; with subsidies, it may not be more expensive than an air-water heat pump.
Anyone who has a general contractor who wants >10,000€ extra simply for the presence of a heat pump effectively has no choice. The offer could also say, "Dear cash cow, not available from me, you take gas and that's final. Best regards." Long live architect-built housing.

I believe the most important thing is proper planning and installation, including hydraulic balancing. Before planning, a heating load calculation must be carried out for the dimensioning of the air-water heat pump/gas boiler. This is even more crucial for the air-water heat pump! After a short search on the internet, you will find many threads like "my heat pump consumes too much, I was promised such low monthly costs."

No one can probably predict how the monthly costs will develop here. If they could, I would recommend intensive stock market trading...

I would like to bring up another aspect to the discussion: The location of the outdoor unit of an air-water heat pump must be well thought out. In my neighborhood, the first legal letters are already being exchanged because of the operating noise (distance from neighbor to outdoor unit approximately 20m). And the system does not seem to be incorrectly adjusted...