KFW, heating demand, heat pumps, consumption

How am I supposed to compare in the end whether it’s worth it.

You can’t. You can only decide whether you feel good about it. Maybe also with the thought that the resale value is somewhat higher (except in 100 years, when everyone has a mini fusion reactor in their basement and the heat pump is gathering cobwebs).

You will only know the actual heating demand after moving in. Nevertheless, you can calculate as described to estimate the cost-effectiveness of the additional insulation. For the annual performance factor, I would assume 4-4.5 for air-water heat pumps and 5-5.5 for geothermal energy: good performance factors come for free, insulation does not. Then include photovoltaics covering 20-30% of the electricity demand and the costs of the feed-in tariff. This changes your calculation and makes the insulation less economical.

Much more crucial than the insulation is the planning of the technology. This costs little to nothing, except for your time. Often you even save money because you then buy more sensible components. You can operate your [Energieeinsparverordnung] house more cheaply than your neighbor operates their passive house with poor planning.

I would build like this today:
- Plan the heat pump’s surface heating very well (trench collector or [Geisha])
- Design the roof for the largest possible photovoltaic system
- Insulation roughly at [KFW 55], depending on costs somewhat better or worse
- Many south-facing windows with good shading, few north-facing windows