Solar collector - heating support or not?

Hi,

I would like to get a few more opinions on the sense or nonsense of solar collectors supporting heating in combination with a condensing gas boiler.

A few key data:
House faces south, located in the mild and sunny Rhine valley with no shade, ~160 sqm living area. NO underfloor heating planned in the living rooms. 24 cm Ytong masonry not insulated, very good (new) windows/doors (will be installed). Roof insulation will be done.

The (NOT independent) energy consultant advised against it. Because when you need the heating, there is usually no sun, or too little – his opinion: maximum annual savings (under optimal year-round weather conditions etc.) ~80-100 €, which would be disproportionate to the investment costs. He recommends support only for domestic hot water.

Sanitary company A said the opposite. Heating support would be the only way, the investment would be manageable since you can also get the BAFA subsidy, but they plan with a ~500-600 L buffer tank and domestic hot water in a flow system.

Sanitary company B said about the same as the energy consultant and said that at least an 800 L tank would be necessary (which is very expensive) and advised me to only support domestic hot water.

Sanitary company C could not or would not give me a clear recommendation, warned me about the costs of heating support (~10 k expensive), but personally has implemented it in his own house and generally supports it, but finally said that only domestic hot water might be more sensible.

The concrete offers with cost breakdown will be sent to me by the companies in the next few days.

So, what do you think?

Regards

We have decided against the heating support. I see the same reason in it as the energy consultant you mentioned. In winter, when you need it, it gets dark early and light late. Often cloudy as well. If every winter were like this one in the Rhine-Main area, it would be worth considering, but the investment seems disproportionate to us for our single-family house.

How big is it and how much space does it take up? ... this 800-liter tank? That's already half a room that you have to plan and build additionally, right?? :cool:

How big the 800 L tank is I don't know exactly either, there is enough space (no new building but existing structure), the problem would rather be getting the thing into the basement and through the narrow staircase, which would ultimately mean having 2 tanks (each 400-500 L) instead or would have to.

Hello,

a thermal solar system for domestic hot water pays off quite quickly compared to the heating-supporting variant.

Without going deeper into the system details (only 800 l buffer storage?), I would choose a system for domestic hot water preparation in your place. Especially if no underfloor heating is present in the house. The return temperatures of conventional radiators do not contribute to the efficient operation of the solar system.

Oh yes, new radiators are also being installed: Kermi x2