Does it make sense to install an air conditioner?

I would also prepare or install one. Possibly directly with [Photovoltaik], because then you come out relatively cost-neutral. That would definitely be quite good. When the sun shines, there's electricity. And by chance, you can then cool. How practical.

Hehe, yep finally a meaningful task for photovoltaics.

I would make it dependent on which direction the rooms face and whether there are enough windows for ventilation. I usually only sweat indoors during the day in summer when the air is stale. In the bedroom - unfortunately with south-facing windows - there is a ceiling fan above the bed. It is wonderful.

Photovoltaics and air conditioning are a good combination - although I would never set the rooms to a temperature that feels like a fridge, but always just a few degrees below the outside temperature. Otherwise, I quickly get a sore throat.

The question is which temperatures are comfortable for you? If it is 30°C outside, I don't want 20°C inside, because that inevitably leads to a cold for me. In our well-insulated new building with automatic shading, the temperatures do not exceed 24-25°C. That still feels comfortable; coming in from the midday heat outside, it feels cool. I sometimes cool the bedrooms with the underfloor heating (cooling). For me, the answer would therefore be that an air conditioning system is unnecessary.

That depends on a lot of factors. But if the possibility exists, I would have the holes and possibly also the cables installed in the bedrooms. It won't be cheaper than when building the house.

We have automated venetian blinds and at night the controlled residential ventilation switches to bypass mode if the outside air is cooler than the inside air, in order to cool somewhat through that. So far, it is quite bearable.