Problems with the alignment of our planned solar installation

Unfortunately, solar thermal is sold by the developer at a certain price and installed with poor technical implementation... You notice this when appropriate protective measures do not work because there is too much hot water in summer, or the circulation is so poor that the pipes are loaded to the limit... In the end, the system breaks down after a few years (the warranty just barely outlasts the system). Then it becomes a money pit.

Speculations...

I am simply assuming now that there is no heat load calculation either, since the heating (gas/oil) is massively oversized. Comment on that: we always install it...

You are most probably on the wrong track...

P.s. a domestic hot water heat pump also works without photovoltaic. But photovoltaic is even more suitable in this case.

Why? Because it becomes a money pit just like the ST?

By the way, photovoltaic pays for itself.

Hmm, yes exactly...

With solar thermal I save some hot water costs for the normal heating.

Yes, about half of the year, and you can also have up to 70 degrees in the tank on sunny days and even use it to "heat the pool for free" if needed.

With photovoltaic I save electricity and even get money for the surplus... But: connected with a bit of paperwork (tax office/DSO...)

But you have to invest much more money for it to be worthwhile or at least break even after a few decades.

I would be interested in the costs for solar thermal.

They are generally on the same level as the costs of a domestic hot water heat pump. So about 1500-2000 as well.

The installation effort also amounts to 3-4 hours for 2 workers.

You see... no matter which dummy system you choose to meet the requirements, the costs for ST or domestic hot water heat pump are the same. Only with ST you then have hot water when the sun shines without extra costs.

With the heat pump, you either need electricity from the outlet or an additional photovoltaic system on the roof, which also costs extra money and effort. (Second meter, business registration, etc.)

Speculations...

You are most likely on the wrong track...

Why? Because it will become a money pit just like the ST?

Hmm, yes exactly...

Yes, about half of the year, and on sunny days you can have up to 70 degrees in the storage tank and can even use it to "heat the pool for free" if needed.

But you have to spend a lot more money for it to be worthwhile or at least to break even after a few decades.

They are generally at the same level as the costs of a domestic hot water heat pump. So also about 1500-2000.

The installation effort also amounts to 3-4 hours with 2 workers.

You see... no matter which alibi system you choose to meet the requirements, the costs for ST or domestic hot water HP are the same. Only with ST you have warm water when the sun shines without extra costs.

With the heat pump, you either need electricity from the socket or an additional photovoltaic system on the roof, which also costs extra money and effort. (Second meter, business registration, etc.)

That a developer wants good for someone is very, very unlikely in my opinion. Ultimately, he buys the service as cheaply as possible = his margin, and beyond that he has to calculate x% as warranty. Regardless, ultimately everyone must decide for themselves what fits.

A photovoltaic system is still worthwhile.
You just have to compare offers (as with many things) – when you have reached a price in the range of €1100-1250 net per kWp, then such a system pays off with 30% after about 7-8 years. After 5 years you can switch to the so-called small business regulation with the tax office, then the self-consumption doesn't cost you anything "tax-wise" anymore.

Contrary to pub talk opinions.

I have had a photovoltaic system for 1.5 years. A neighbor is now also building one, and in our development area there have been many retrofits in the last 5 years and recently also some who installed it directly during new construction.

P.S. The first neighbor is throwing his solar thermal system (tube variant) off the roof again after almost 7 years. Warranty expired, tubes leaking, spare parts no longer available (manufacturer bankrupt), alternatively only parts with replacement of the entire modules...
What’s coming on the roof now? A photovoltaic system.

Strictly speaking, there is still the possibility to install one collector each on the east and west roofs, switching is then done with a changeover valve in the return flow. From 25 years of professional experience in this field, however, I can tell you: such small solar thermal systems never pay off, they are just good for meeting requirements or for a clear conscience. They also save a few operating hours of the main heat generator from May to September, so it lasts a bit longer. Overall, in my opinion, in the long run—if financially possible—a photovoltaic system with a BWWP would be the better solution.

@

No one questions that it works for you. But it helps the OP very little, especially with east/west orientation. Between the lines it says: How can I comply with the energy saving ordinance with as little time/money/planning effort as possible. And the answer is definitely not: build even more unnecessary technology etc. in and on the house. Rather, just slightly enlarge the already planned system or simply have it recalculated.

Exactly. He clearly said: as cheap/inexpensive as possible!

Even if this deviates somewhat from the actual problem, I find the resulting discussion very interesting. Even if this may be incomprehensible to some, I will briefly describe our side of the story.

My wife and I both work in commercial professions and are therefore completely far removed from the construction industry, and being under 30, we can hardly draw on private experiences in these areas. Our parents built their houses more than 20 years ago, which is hardly of any help. This also means that this subject matter is completely foreign to us.

For these reasons, we consulted 5-6 selected construction companies last year. Everything was included, from the complete solution with photovoltaic system, heat pump, controlled residential ventilation with heat recovery, various KFW packages, etc. We decided on the developer with the best recommendations from our environment, from whom we can get everything but are not obliged to take anything. The companies for trades they do not perform themselves (electrical, heating, windows) all come from the area and are well known.

I like to deal with certain topics and am also happy to get opinions from others out of personal interest – as in this forum. What I certainly do not presume is that I then know the respective area thoroughly; I do not have to. I just want to make my decision to the best of my knowledge. In the end, it is also the job of the construction company to get me or us on the right track. I chose another profession, which I do well, but building a house is not part of it, so I have to rely partially on those who do it every day.

If I did not trust the developer now and it was only about “the easy solution with the largest profit margin,” then I would have already made a mistake during the pre-selection. For example, the chosen company has no catalogs or an internet presence and lives solely on recommendations – they have a big reputation to lose with us and will pay close attention to that.

In the end, we decided on a variant that is certainly very simple for many of you, with a gas condensing boiler and underfloor heating. In addition, good windows with a U-value of 0.6, a properly insulated base and façade, and the described solar system to support hot water. The chosen components are nothing special but proven and qualitatively high-quality in their area.

Besides the fact that we partly think more conventionally and some modern techniques did not convince us, the budget certainly also plays a role in the end. There may be people who pay off half a million euros with 1% repayment and don’t worry about everything around it. We are far from that and feel completely good with our decision.

Now small problems like this orientation arise, which we will solve. I am grateful for the point that the planned system can possibly be expanded in terms of area to meet the requirements. At the beginning of next week, the developer will present us with his solutions – we are curious and may have some approaches to solutions to incorporate by then.

I will gladly report on what came out of it :)