[BeetleB]

On the flip side, window AC's are really effective at cooling the single room they're in.

In the wooden house I have, I just can't get the room that cool if the temperature is in the 90's, because the internal walls provide very little insulation. It was trivial when I lived in concrete buildings. It's a ridiculous waste to have to use central air conditioning to cool a whole house when I really just need to cool 1-2 rooms.

[CalRobert]

OK, but window AC and also mini and multi split systems, which are also like this, work just fine in wooden houses, so I don’t see the connection. I had multi splits in a wooden house in Ireland.

Edit: re-reading… I guess it depends on the house but I definitely have had a substantial temp difference between rooms in a wooden house

[BeetleB]

We may just have different standards on what "cold" means :-)

Let's say it's 35C outside. Just using a window AC alone, I want to cool the room to where I'm uncomfortably cold (not quite shivering but close) - within about an hour of turning it on (2 hours max). I can't do that with my wooden house in the US when the outside is that hot. I can make it comfortably cool, but no cooler.

(I had better experience in a wooden apartment building, but that's likely because the walls between apartments have insulation).

Actual numbers: If I leave the AC on at max cool all night, I can get the temperature down to 20C. Keep in mind that it's cool outside at night (and actually will dip below 20C at some point at night).

I've never gotten it below 20C.

When I lived in a concrete place, we would never set the thermostat on the window AC to the coolest setting - it would get too cold!

(Yes, I clean the filter and have even replaced the AC - the unit wasn't the problem).