Is preparing for an air conditioner worth it?

That was not the point of the last question at all. It was about whether the installation of an air conditioning system alongside the heat pump can be detrimental to achieving a KfW standard.

Unfortunately yes, energy consultants used to turn a blind eye to this, but nowadays that is no longer possible. Up to two devices can be covered by photovoltaics; from the third device onwards, you lose the funding completely. Since we ourselves are currently in the planning stage, these are reliable statements at least for a 55 standard house. We will probably first just lay the wiring and then wait through the first summers. If it really becomes unbearable, we will see if we install it anyway.

Up to two devices can be capped by a photovoltaic system; from the third device onwards, one is completely excluded from funding.

Since often only one device is sufficient in modern single-family house constructions, the clause is rather pointless.

Since often only one device is sufficient in modern single-family house constructions, the clause is rather pointless.

But even one device must be capped by a photovoltaic system. And the energy calculation must be redone.

Do you have any evidence for that?

No. It would just surprise me if there were a connection. Whether I cool with the built-in heating heat pump or - more efficiently - with a split air conditioner, does not change the theoretical energy demand of the building. Maybe the actual demand changes (in whichever direction), but that is not decisive for the KFW.

Regarding the Bafa subsidy: Last year, private systems were also subsidized. However, the addition "mainly for heating rooms" was already included. Since a lot has changed with subsidies, it may be that the subsidy no longer exists. And it may also be that new buildings were excluded. Which does not change the fact that air conditioners are initially recognized as an efficient heating system.

By the way, I would not agree with this part:

And since a lot of electricity is required for air conditioners,

Of course, that is a matter of opinion - but in proportion, it is not much energy. I have about a 10:1 ratio, heating energy to cooling energy, both in a new building and an old building. In numbers, that is 500 kWh for a 140 sqm old building and 200 kWh for a similarly sized KfW70 new building (at approx. 22-23°C RT).

We have an air conditioning system and wouldn’t want to be without it again. I would definitely have it prepared at least. Summers will potentially get even hotter in the next 20 years.

Thick pipes run through the walls for the air conditioning with us for the condensate water that has to drain away. I’m already glad to have that installed flush with the wall. We have 3 split units on 150m². One in the living/dining/cooking area (open plan), one in the office, and one for the entire upper floor (bedrooms). We run the unit on the upper floor during the day in summer when the sun shines (because then we generate energy via photovoltaics) and open the doors to the bedrooms we want to cool. That works well for us; the air is also circulated in the house due to the airflow from the ventilation system. With this approach, I can only recommend not placing the split unit too close to the stairs like we did. Because even if cooling works well, cold air wants to go down, and if there’s a staircase there... well, our hallway in the basement is always very pleasantly cool in summer. :D

Are there any experiences in the community, or are these empty "threats" from the KfW?

It's similar to the tax office or toothache....... it may come, but it may also not come.......

Why should an air conditioner worsen a building's energy efficiency? They are promoted by the Bafa because they IMPROVE the energy efficiency of buildings.

I can only say from current experience that just installing the air conditioner would have destroyed the KfW standard for us. We had exactly this problem 8 weeks ago. The energy consultant recalculated the building under this condition according to a different DIN (at least that's how I understood it) and initially it was NOT sufficient; at some point/somehow, however, according to him this other recalculation was absolutely necessary.