ᐅ How to Achieve KfW40 Standard? Energy Systems and Cost Efficiency

pagoni2020 schrieb:

That sounds reasonable, since having a reliable general contractor (GC) is already half the battle and saves you a lot of trouble and energy 😀 !!!
Regarding photovoltaic systems, there’s a forum you can easily find on Google. In my opinion, they mostly speak “technical jargon” there… luckily, it’s a bit more straightforward here, which suits a down-to-earth person like me.
A photovoltaic provider was already mentioned to you earlier in this thread. If you involve the GC’s electrician as well, that would at least be a good start. In our case, the GC’s electrician made a very good offer, and we will probably accept it because then everything comes from one source. Maybe it would be slightly cheaper elsewhere, but having everything from one provider is more important to me.
In the other forum, the prevailing opinion is that photovoltaics always pay off and you should size the system as large as possible, even beyond 9.8 kWp if feasible.
Ultimately, there is no one-size-fits-all calculation; we will achieve KfW 40 Plus only because we wanted a high insulation standard anyway; we will have to install a battery storage in any case, which is almost fully subsidized through the plus incentive.
As has been mentioned here sometimes, you can make a battery storage look good or bad depending on how you calculate it. There are thousands of opinions about the modules—some offer longer warranties, others more output, others better prices… For me, reliable implementation is very important. It’s like with cars: there are justified reasons for everything from a Dacia to a Lexus.
For us, it will probably be Solarwatt modules with a 30-year warranty and glass construction, because the electrician sells and knows them, and they are supposed to be good; but other providers have their advantages as well.
In your case, it might be difficult to build a budget house now for your parents that they will later live in as a desired KfW-xy energy-efficient house.
Just a gut feeling suggests building the house for your parents now according to current energy standards without additional KfW measures; that way, you already have a very good house. The parents may consume little energy anyway and thus are inherently economical. If you want to live in it later… who knows what life will bring, and only then would I implement the best possible measures available at that time, whether photovoltaics or something else. Until then, today’s technology will already be outdated.

Hello, if you receive subsidies for the battery storage and photovoltaic system, you are not allowed to feed electricity back into the grid. Furthermore, the feed-in tariff for a photovoltaic system without subsidies only applies for 20 years, so it is sufficient if the modules have a 20-year warranty since the system would typically be replaced after that period. At least this was the case under KfW 153; how this will be with the BEG is still unclear, so we are waiting, including with construction. Happy New Year.

• We would like to achieve the KfW 40 standard. What measures would you suggest or consider mandatory?

- thermal envelope with at least 42.5 cm (17 inches) thick masonry (preferably brick rather than aerated concrete, etc.)

• We have read very positive reports about the economic efficiency of photovoltaic systems with east-west orientation on flat roofs. How do you assess this compared to our maximum 30-degree (30°) pitched roof? And is 25 or 30 degrees better?

- ask here in the forum, possibly consult a solar cadastre, calculate shading, orientation, and system design with PVSOL. No satellite dish or windows on the roof—fully roof area use 😉

• Does a battery storage make sense?

- opinions differ, and the facts are clear: generally no, it is an expensive gadget. For KfW 40+ under the BEG program, it is no longer strictly required, as the focus in residential buildings is on achieving certain energy values rather than specific technical equipment.

• Are there module manufacturers you particularly recommend?

- Heckert, Q-Cells, LG, and many more.

• Can you recommend an energy consultant or an expert for installing photovoltaic systems in the Ruhr area/Sauerland?

- sorry, no, I don’t know anyone there. We are from Saxony.

user386dx schrieb:

Hello, if you receive subsidies for the thermal storage and photovoltaic system, you are not allowed to feed energy back into the grid.

For which subsidy is that supposed to be the case?
This statement is incorrect for KFW153 -> 60%+ soft

RotorMotor schrieb:

For which subsidy is that supposed to be the case?
For KFW153, this statement is wrong -> 60%+ soft

Hello, sorry, I meant, for example, sealing at 273 at 50% and at 153 at 60%. Although that is now changing.

Best regards

user386dx schrieb:

Hello, if you receive funding for the battery storage and the photovoltaic system, you are not allowed to feed electricity back into the grid.

Thanks for the info!
If I reach KfW 40 Plus through building measures, the construction is subsidized, not directly the purchase of the photovoltaic system or the battery storage. As far as I understood, for KfW 40 Plus, I was “required” to include a battery storage. So why would feeding electricity into the grid be prohibited? We are in Saxony, and there is no significant subsidy for the battery here.
Am I mistaken? Where does it say that feeding in electricity is not allowed?

user386dx schrieb:

That’s why it’s enough if the modules only have a 20-year warranty, since then you replace the system.

In 20 years I will be over 80 years old… so this question is less relevant for me. Also, I don’t have to replace something just because the warranty expired. From a purely logical perspective, many technical systems are already outdated and technically superseded after fewer years. The 30-year warranty is not a decisive factor for me, although it does suggest good product quality; I will probably decide based on the electrician who sells the product. I would consider it even if the warranty were only 20 or 15 years.
Could you please provide concrete sources for your statements before I search endlessly? That would be really helpful.

user386dx schrieb:

Thermal envelope with at least 42.5 bricks (preferably clay bricks rather than aerated concrete, etc.)

For us, 36.5 bricks work as well, and yes, aerated concrete is more difficult or hardly feasible. Whether to use a filled 36 cm (14 inch) brick, a 42 cm (17 inch) brick, or external insulation — in the end, that is a calculation for the energy consultant. For our build, it will be 36.5 cm (14 inch) bricks plus various insulation measures.

user386dx schrieb:

Whether a battery makes sense is debated, and the facts are clear: no, it doesn’t. It’s just an expensive toy and not clearly required anymore for KfW 40 Plus under BEG. For apartment buildings, it is more about achieving certain energy values rather than specific “technology systems.”

Sorry, I can’t find that information myself. Maybe you could help with sources?

RotorMotor schrieb:

This statement is incorrect for KFW153 -> 60%+ soft

Am I correct in assuming that if I build according to Kfw153 or Kfw40Plus standards, I need a storage system among other things, but I am still allowed to feed energy into the grid? Provided I receive a subsidy from the federal state for the storage system, this would not hinder either the feed-in or the subsidy in general. Is that right?

user386dx schrieb:

For certain system sizes starting at 25kWp, remote controllability applies; below that, a 70% curtailment limit.

In simple terms for beginners, what does "curtailment" mean and what are the consequences?
Our system will probably have at least 9.8kWp, maybe a bit more, but not 20 or 25.