Renovation of a 1960s house: Questionable expert recommendations?

And unlike fossil heating systems, you can very easily produce the "fuel" yourself with a heat pump.

Aha, like with photovoltaic in winter?

not to forget the photovoltaic system which first has to be financed with a few thousand...

Aha, about photovoltaics in winter?

Yes, of course. To a much greater extent than own oil production.

not to forget the photovoltaic system that first has to be financed with a few thousand...

At least you don't have to pay it back yourself.

I do not know of any photovoltaic system offer so far where I would get the photovoltaic for free and with profit. If you have a provider who promises me a profit without tax trick bookings, then please post it. Gladly as a private message.

You probably always include a storage system. That makes every installation unprofitable.

The calculation is quite simple: You look on a website (I’m not allowed to name it here, the mods are strict) to see how much yield you get per year at your location from your roof pitch + roof orientation. Calculated per kWp, that might be 1000 kWh/year. You multiply this by the expected feed-in tariff of maybe 7 cents, times 20 years. In the example case, that’s 1400,-€.
This is the price that a purchased and installed kWp without tax must not exceed. This ensures that the system pays for itself 100%.
Beyond that, you make an additional (currently) 20 cents profit per self-consumed kWh. Depending on electricity consumption, that’s a few hundred euros extra per year.
And after 20 years, the system still runs and reduces your electricity bill. By then probably with storage for a large part.

So currently, EVERY photovoltaic system is a profitable business if you leave out the storage and can build at least 8 kWp.
Important: the bigger, the cheaper the kWp becomes. And everything under 100 kWp is NOT too big.

well this loophole will eventually either be exploited even more by other market participants or the state will simply reduce the feed-in tariff for small entrepreneurs to 4 cents... over 20 years a lot can happen and if you are banking on that, I would find it too risky. Or do you see it differently?