Alternatives to gas, how are they calculated?

Gas and solar thermal, simple, cheap, uncomplicated and if the insulation is good then the consumption is a joke.

azu ein Gasanschluss für einen unbekannten Preis

Is that so? The payback period is – if I remember correctly – about 15 years (gas vs. air-water heat pump). Admittedly, quite general, but as a rough estimate. However, here often only the boiler vs. heat pump and the corresponding consumption are taken into account. The fact that you necessarily need a chimney for gas, which costs money, is often not modeled. Maintenance costs for heat pumps are also often complained about, but the regular visit of the chimney sweep is omitted.

For me personally, it makes little sense to rely on a depleting energy source (crude oil, natural gas) that will inevitably become more expensive. Sure, certainty comes from looking into the crystal ball, but it is currently broken.

I also actually considered gas once, I do not want to demonize it, but to pretend it is the only sensible and economical solution is simply nonsense. It depends too much on the framework conditions what is economical (usage behavior, number of residents, insulation standard, house location, etc.)

That is not entirely correct. The required renewable shares could also be covered via PV, for example if one decided on a gas boiler without hot water, and hot water through electricity/instantaneous water heater. But it would not be economical. PV is much too expensive compared to solar thermal. I think you pay a 200% surcharge

And with us, electricity, water, and gas cost less than just electricity & water. Only 2T for all 3 things, instead of 2.4T up to 10m