Difference in purchase cost between gas pump or heat pump

That is exactly what I wanted to express. The possibilities are already there to operate a gas heating system in a very climate-friendly way. It depends on the politicians. (just like with cars... climate-friendly synthetic fuels - completely without petroleum - have been researched and could easily be used in current combustion engines, saving 60-70% CO2. Unfortunately, this is not desired at all, because, absurdly, the focus is entirely on batteries *sick*)

The federal government probably sees it differently... or why else are billions being spent on the construction of Nordstream2?

Regarding fossil fuels and the climate debate: Likewise, the existing natural gas grid could also be (partially) supplied with biogas in the future.

Because money can be made with it and accordingly many existing buildings rely on gas. That will not change overnight. Apart from that, the pipeline is built and maintained by the private sector, not by the state.

Biogas is at least a moral problem if agricultural land is specifically used for this purpose instead of growing food. The efficiency is also an issue, although not as much as with the dud hydrogen, whose production is simply far too expensive.

The CO2 price was set at €25/t from 2021. That corresponds to about €75 for 12,000 kWh of gas per year. It will rise to €55/t or €160 by 2025.
From 2026 it will be recalculated annually.
The Swiss have already gone through this; after the ramp-up phase the CO2 price currently went up to about €90, as far as I know.
Electricity will be relieved in return.

Yes, €100 more or less per year does not compensate for several thousand euros in acquisition costs. In my opinion, gas heating is still not an obsolete model as of today. In 10 years it will be different, that I dare to predict.
However, I would already try today to limit the impact, i.e. prepare the building for another energy source (structural conditions for split heat pump, design underfloor heating for low flow temperature) and reduce consumption (insulation + controlled residential ventilation). Those who need little energy are not interested in rising levies.

A gas heating system does not necessarily require a chimney (Schornstein). Our heating system is in the attic and has only a very small exhaust pipe.

@guckguck: you are absolutely right. The joke is also that natural gas is subject to a CO2 price, but the electricity price for the heat pump is supposed to decrease... even though the electricity will come from coal power plants until 2038 (the CO2 balance for coal power generation is worse than for natural gas)

@guckguck: you are absolutely right. The joke is, moreover, that natural gas is subject to a CO2 price, but the electricity price for the heat pump is supposed to decrease... even if the electricity comes from coal power plants until 2038 (the CO2 balance of coal-fired power generation is worse than that of natural gas)

There is no joke to be found in that. After all, we are talking about a comprehensive restructuring of existing infrastructure. Transition phases, times, and technologies are quite normal in this context. One should not view this from a here-and-now perspective, but rather medium to long term.
In addition, electricity is supposed to become cheaper by reducing the Renewable Energy Sources Act levy. That does not exclude the possibility that electricity tariffs with fossil fuels become more expensive, since CO2 charges will be applied there (either directly shown in the electricity price or included in the producer price).

I would already try today to limit the impact, i.e. prepare the building for other energy sources (structural conditions for split heat pump, design underfloor heating for low flow temperature) and reduce consumption (insulation + controlled residential ventilation).

Are there other points besides the underfloor heating with low flow temperature to consider when building a single-family house in 2020 with a planned gas heating system, so that one could switch from gas heating to a heat pump if necessary in a few years?

If you plan a basement with a relatively large heating / equipment room, what else?