How to achieve KfW40? Energy technology / Economic efficiency

Thank you for the information! If I achieve the Kfw40Plus through structural measures, then the construction is subsidized and not directly the purchase of the photovoltaic system or the storage. From my previous understanding, I was "forced" to include a storage with Kfw40Plus. Why should feeding in then be prohibited? We are in Saxony and there is no very high subsidy for the battery. Am I mistaken? Where does it say that one is not allowed to feed in then?

In 20 years I will be over 80... so this question is less relevant for me. Besides, I don’t have to replace something just because a warranty has expired. Purely mathematically, many technical systems will already be outdated and technically surpassed after fewer years. The 30-year warranty is not a decisive feature for me, although it rather speaks FOR a decent quality of the product; I will probably decide on the electrician who sells this product. So I would also accept it if it were only 20 years or 15. Could you please give me concrete sources for your statements before I go searching endlessly? That would be really nice.

It is also possible with 36.5 for us, and yes, aerated concrete rather difficult/hardly possible. Whether to use a filled 36-cm brick, 42-cm or external insulation... all of this is ultimately calculations by the energy advisor. For us, it will be 36.5 brick plus various insulation measures.

Sorry, I can't find this anywhere, maybe you could help with sources.

Why is an aerated concrete wall with 24 cm thickness plus 12 cm WLG032 insulation board not enough for me? I come to a U-value of 0.167. Proper perimeter insulation and roof insulation added, good windows together with an entrance door system, controlled residential ventilation plus geothermal heat pump and possibly photovoltaic. I should be on a good path with that. Besides the aerated concrete belief war, which I don’t want to start here. I know the endless discussions.

By the way, I have been living for 9 years in an aerated concrete house with 17.5 cm wall thickness plus 12 cm WLG035 insulation boards with a wall U-value of 0.20 and am very satisfied.

For blondes in simple terms, "Abregelung" means? or what are the consequences?

Quite simple: Max. 70% of the nominal power is the possible maximum feed-in.

[*]We would like to achieve the kfw40 standard. What measures do you suggest/are absolutely necessary?
[*]We have read very positive texts about the economic efficiency of photovoltaic systems with east-west orientation on flat roofs. How do you see it with our max 30-degree pitched roof? And is 25 or 30 degrees better?
[*]Does a storage system make sense?
[*]Are there module manufacturers you would particularly recommend?
[*]Can you recommend an energy consultant and/or an expert for the installation of photovoltaic systems in the Ruhr area/Sauerland?

Do you want to take the subsidy or build the best standard? Depending on what your considerations are, the recommendations differ.

East-west systems have the advantage of generating electricity for more hours per day but less during peak times. For some consumption profiles, this is good for increasing the self-consumption rate and thus economically sensible. The flatter the solar angle, the more favorable a steeper tilt is. However, I would not push this to the extreme in a residential building, as the appearance of the house also plays a big role for me.

Storage: Calculate yourself and understand the influence of the basic assumptions. Depending on the basic assumptions, a storage system is worthwhile or not.

The modules are now quite well developed, and there are many good manufacturers. If the appearance of the house is important to you, you can consider that when choosing the system. We chose solar tiles from Autarq – of course, the design costs extra.

Clensolar. But they come from eastern Germany. Great company with good prices.

Or Actensys, but they come from southern Germany...

Whether a storage system makes sense, opinions differ and the facts are clear here, no it does not,

“The others have an opinion and I have facts.” Funny dialectic reminiscent of a departing head of state. I agree on the following point: The opinions differ. This is due to the underlying assumptions about cycle frequency, degradation, consumption curve, lifespan... Nothing “facts,” all assumptions that can be debated thoroughly. There is plenty of evidence for economic viability and non-viability because not every system with storage operates under the same conditions. Therefore, a general statement is – as is currently fashionable – strongly oversimplified.

Putting aside the aerated concrete belief war, which I don’t want to start here. I know the endless discussions.

I am a pacifist, so I wouldn’t want to participate in an aerated concrete war.
I always!!! hold the opinion that feeling comfortable in a house does NOT depend on nominal values etc.
I have lived comfortably and nicely for 30 years in a normally built Poroton house, colleagues of mine in wood and aerated concrete were also satisfied. I’m out of the war_O
Between the days, a lot was calculated by the energy consultant and it usually depended on the building envelope. I had pointed out here that it is NOT necessarily required to have a 42 cm block, because we are also staying at 36.5 cm in brick. Ultimately, especially roof insulation (external insulation), floor slab, etc. were adjusted until it fits. I don’t have details yet.
In my opinion, aerated concrete with the same thickness has lower values, which is why I assume and wrote it that it could be difficult/hardly possible, that is in the subjunctive. Above all, however, the achievement of the overall values depends on a variety of corner points and the statement: "it only works with 42 cm and more" is not correct.

Then I should be on a good path

Yep, still the energy consultant has the bible in his hand for you. As I said, I usually only implement measures that I would have done anyway without KfW.

A blanket statement is therefore— as is currently fashionable—strongly shortened.

Exactly, the stone, the insulation system, etc., everything has to fit the project and—above all—that I fit!
Even if a storage system might not necessarily pay off for me in calculations, I might still use it; I would enjoy using some of my own energy myself in the evening. Added to that is the often ignored, individual lifestyle.
The more dismissive description of the storage above as "plaything" I would not accept generally. If I did not implement any "playthings," every house here would look different and cost much less. Our houses and our lives frequently ARE so-called playthings. A storage system is certainly more meaningful than many equipment features that simply contribute zero in calculations. Nevertheless, you can have it.

Electricity storage is deficit.

Not wrong.
However: Also deficit are cars, fancy items, houses, beauty products, clothing choices, more than 4 forks + knives, a new phone... simply everything. If you applied this standard to your life, you would have to stand there in a loincloth o_O. The storage might give back less than it costs in many cases but it still gives something back. Your car burns money from day one, ergo in my opinion that is a blanket killer argument.
In my opinion, life consists of more than just calculating processes, which you can also design according to your needs!
You are right—and at the same time wrong.

We used solar tiles from Autarq - of course the design costs extra.

Hello, this is an in-roof system and therefore more expensive, more complicated (cooling & underroof), high efficiency losses and last but not least: warranty issues.

Everything is understandable. We are not that far apart. I also don’t have to achieve a value at all costs.

By the way, I’m still considering whether to use the above-mentioned wall construction or a 42.5 cm aerated concrete block without ETICS. Building monolithically appeals to me..., but as of now I really have no idea about the percentage increase in costs for the shell construction.

Since the general contractor builds exclusively with aerated concrete, it will definitely remain with the block. I’ve simply had good experiences with the guy. And that counts too...