Roof with photovoltaic or other investment, any experiences?

Thank you very much for the answers so far. After discussions and further considerations here with my people in the house, we come to the conclusion that the money should first be invested in insulation/heating. Photovoltaics can come later when the storage systems are cheaper and electric cars have reached normal price segments.

Could you please explain why you come to this different conclusion? There are certainly some who are considering, reliable figures would be very helpful.

What exactly do you want to know? My plan is a photovoltaic system with battery storage and an air-source heat pump with underfloor heating. Furthermore, planning is underway for an electric car.

Well, your payback calculation. Acquisition costs, expected savings, etc. We also had a photovoltaic system prepared and are now considering investing the remaining buffer in it. But when I look at the average returns per month, and then the average consumption per month of a heat pump of the same type as mine, there is just a gap. How did you solve that?

My first decision was. I am an electrician by profession and do not want gas. That leaves not much besides heating. The next consideration was what the system change would cost me. In my case, almost €6,000 additional costs. Then I decided I want a photovoltaic system. Consideration without or with storage > obtained offers. With almost the same generation capacity, another €9,000 difference. The change from a conventional gas heating system with radiators to an air heat pump with underfloor heating and a photovoltaic system with storage costs about €30,000 in my case.
The payback period of the photovoltaic system is about 13-14 years depending on whether with or without storage. However, I did not deal with the payback period. It is simply like buying a car where electric windows and air conditioning just belong. You either want it or you don’t.
What I looked at more closely was the forecast consumption versus self-generation. It is said that you can achieve up to 80% self-sufficiency degree with a simple storage. My system has a calculated generation of about 7,000 kWh. I hope to be able to consume about 4,500 - 5,000 kWh myself. The total estimated consumption of the house should be under 8,000 kWh. Currently, you get 12.21 cents for feed-in per kWh and the costs are about 18-22 cents for consumption. It is clear to me that I have higher consumption in the winter half-year and must factor that in.
One note regarding this: the system should be under 10 kWp. Self-consumed solar power from small systems up to 10 kilowatt capacity continues to be exempt from the Renewable Energy Sources Act surcharge.

Then I followed, I want to have a photovoltaic system.

Of course, you can do it that way ;-). The opening post does say "invest" in the text. Therefore, I see the question more like this: I have 10,000 euros (or amount X) that I want to invest. What should I do:
- Photovoltaics
- Shipping containers
- Closed real estate funds
- Overnight money
- Professional training
- Football betting
- ...

Possibly photovoltaics will come out on top, in any case you should consider the overall situation of your finances. And you have to set a goal, it can be plain return, but it can also be: own electricity. Some also make investment decisions to "save taxes" ...

For our new build, we initially also planned photovoltaic and battery storage. Basically, it fits well with the heat pump and I hoped for subsidies.

Since photovoltaics do not mean an increase in comfort, I calculated it as a normal investment. And it quickly became clear that the battery storage never pays off and the photovoltaic system (with maintenance costs of 2%, electricity meter fees, tax on self-consumption, etc...) will probably only break even after at least 18 years, and that only if the inverter "survives." If this investment is financed through a construction loan, the outlook is very bleak.

The calculation naturally depends on electricity costs, self-consumption (tax!), and feed-in tariffs. The fact is that electricity prices on the market are very low and will probably not reach old levels again in the next 10 years. Consumer prices are mainly driven by taxes. Political decisions have also been made to cap the Renewable Energy Sources Act. That means taxes will rise further in the short term but probably not in the medium term.

Brief addendum: I ended up laying 2x 40mm conduits on the roof to be able to retrofit in 10 years if necessary. I also think empty conduits make sense for the garage.