Solar thermal and pellet heating, heating support / hot water

Hello,
we are currently planning a new building, living area approx. 150m², solid construction with 35 cm bricks, triple glazed windows, no basement, underfloor heating on ground and upper floor, house with hipped roof, extension with hipped roof with 20° pitch exactly facing south, ETA PU7 heating system with approx. 850l buffer tank, controlled residential ventilation with heat recovery, currently 2 people.

The extension is basically our garage and heating room with passage into the living area.

The plan was originally a solar thermal system with heating support and hot water. After reading a bit here, the shock was great that it is basically wasted money and that actually only hot water production is worthwhile, if at all.
I am concerned with two things, 1. of course to save money sometime in the future, and 2. to protect the heating system somewhat so that it does not have to start up so often in summer.

The heating engineer proposed two solar thermal systems 1. Buderus Logaplus package with 4.7 m² or 2. Buderus Logaplus with 9.5 m²

I am aware that the roof does not have the optimal pitch, therefore or IF it would be worthwhile, I would consider a mounting frame.

Hi

Since a buffer tank is required anyway for the pellet boiler, the step to the collector system is rather small, and so in the summer months and the transition period, the boiler is not in operation for short run times.

I would choose the 9,.. system and mount it on the pitched roof.

Olli

Thanks for the reply Olli, I think the Buderus would cost about 5500 euros, I couldn’t find anything online about the quality/experience. But in this forum the Wolf f3 was recommended, priced roughly the same. Or are there other manufacturers that are worth recommending? I forgot to mention that the buffer tank is the Eta solar sps 825 and there should also be a fresh water module attached. The solar thermal in the size of 9.6 m2 could then also be used as heating support?

Do you even need the ST system? With controlled residential ventilation, it might already be sufficient. It will probably take a very long time to recoup the invested money in a new building at €5500.

Honestly no, I thought it was worth it, but after reading up a bit I was somewhat disappointed. Partly I also want to spare the heating a bit, but considering that the pellet stove costs about 8500 euros and has a lifespan of 20 to 25 years, a solar thermal system for 5000 euros would actually be a bad investment. The one from Wolf with 9m2 would cost 3000 euros, probably less with subsidies...

Can one generally say that a solar thermal system is not worthwhile? The roof actually has a good orientation

Our energy consultant said that at ST the prices have not decreased in line with photovoltaic due to the market volume and that he would, if at all, do photovoltaic plus an electric heating element operated with it in the buffer tank.