Which heating system for the 200 sqm new building?

Anyone who buys photovoltaics for a heat pump can try drawing a coordinate system.

The photovoltaic system pays for itself even without any consumer, purely through feed-in with a decent return. The answer is therefore always: do it, provided it is not a weirdly shaped roof or there are severe shading issues.

If things go badly, the feed-in tariff will disappear next year. Until then, as much and as large as possible goes straight onto the roof. South, east, and west up to 45° have paid off purely from the feed-in tariff within a maximum of 12 years.

And it's just a completely different technical challenge to paint a house than to plan a heating system .... we did a lot ourselves, really, but even we wouldn't have dared to do that ....

With the next house, just be brave. You can find a lot of support, examples, and ready-made plans from other builders online. You just have to be able to understand and argue the plans to convince and find the craftsmen who will then implement them in your interest. I took on the heating system without prior knowledge and otherwise mostly relied on external help. Everything else I tried ended up being more expensive and took longer.

I still don’t understand what use I have without storage, that photovoltaic produces a lot of electricity for me in the summer which I don’t even need, I need it in the winter. Unless I have air conditioners.

We would have been at a 15K investment and had calculated that it would eventually pay off, I don’t remember how many years.....12 or 15 or so.

But that was calculated without considering what breaks. Therefore, we decided to only prepare for it as long as storage systems are still so expensive and we don’t have an electric car.

As has been written several times, you get paid for the electricity. In summer, you don’t need a storage system either; what do you want to do with the electricity at night? The larger the system, the more you can use the little yield in winter.

We would have been at a 15K investment

That would each be a monster system with well over 10 kWp if you have this investment. Gross, it is then already over €18K! With that, you buy yourself a 13-16 kWp system. Respect for your original planning.