Construction costs are currently skyrocketing

That will be quite a large solar thermal system that can still support the heating well in winter. I seriously doubt that it won't be worth it.

If he renovates the heating now, he will hardly switch to heat pump+photovoltaics in the next 10-15 years.

So please invest in solar thermal and save a lot of fuel and money over the next 10-15 years.
That makes much more sense than a photovoltaic system, because hot water can be stored cost-effectively.

This heat pump and photovoltaic hype here in the forum is really annoying sometimes.
If you only know a hammer, you see every problem as a nail, right?

In hindsight, I found the underfloor heating expensive because it's "no" work for plumbing... We could have done it ourselves.

That would always be worth it to me for the transfer of the warranty risk. The water damage from a neighbor's leaking underfloor heating is warning enough for me. :D

That will be quite a large system, which can still support the well even in winter. I strongly doubt that it’s not worth it.

If he renovates the heating now, he will hardly switch to heat pump + in the next 10-15 years.

So please invest in solar thermal and save a lot of fuel and money over the next 10-15 years.
That is much more sensible than a photovoltaic system, because the hot water can be stored cheaply.

This heat pump and photovoltaic craze here in the forum is really annoying sometimes.
If all you have is a hammer, every problem looks like a nail, right?

In winter, when it’s dull and gray^^
Enjoy.

My photovoltaic system is at zero after almost 7 years and then it really takes off;-)

Hot water when you don't need it and no hot water when you would need it for support in winter. ST is greatly overrated. Better to use photovoltaics and a water-to-water heat pump. To make it worthwhile in 10 years, you would need to save €1000 per year. That is completely unrealistic.

Next offer from an established company: 167€/sqm for insulation with rock wool (!) and not EPS.

Incredible what prices these are I come from the construction sector, normally it's about 90-100 euros / sqm Your companies must be making good money :-)

Crazy what prices
I come from the construction sector, normally it’s about 90-100 euros / m2
Your companies must be making good money :)

Normal is always relative. In Cologne, 2-3 years ago, 150/sqm with scaffolding and value-added tax was probably already common. Where do you get the service for 90-100? With everything included?