By all means install an AC unit to deal with the worst of it. Just install shades as well when you've got the scaffolding out so you can install a smaller, cheaper, and less energy-hungry one.

Unfortunately I personally live in a highrise, and in a rental unit, so that "small hole and a bracket" definitely isn't an option for everyone.

If you can open a window at all you can run a portable AC unit. Even just 3-4 inches is enough.

European windows open sideways not up and down. So we can't just stick an ac unit on the window.

Yes you can (I've got one), there are various window seals to adapt to that or you can dyi too. The noise etc make it a temporary solution at best but it's possible.

I've also used portable AC inside my home, it was horrible, a lot of heat creeps in due to bad insulation for the heat exhaust pipe, also creates vacuum since it exhaust air, which in turn sucks in more hot air

You don't stick a portable AC unit in the window. The unit sits inside. You just run vent hoses out the window for the compressor.

Opening sideways also shouldn't matter for a casement AC unit.

Portable ACs are borderline scams because the hot side is inside the room it's trying to cool, among other reasons[0].

[0] obligatory TC rant: https://youtu.be/_-mBeYC2KGc

That's a perfectly good way to waste kW of energy every day and make the heat outside worse.

It may waste energy, but if so, it's wasting y kwh of energy per day (or joules), at a probably-variably rate of x kw, where y is x * 24 (for kwh)

Sure beats heat stroke and death.

You are just moving heat strokes elsewhere.

Hell, people are dying now in Europe in part because US AC abuse burned so much energy it contributed in a large part to global warming.

I doubt AC "abuse" is relevant compared to just about everything else contributing to global warming.

You'd have to have your windows open at all times with only a thin fabric blocking the opening to do that with most european windows. And then you still have your compressor inside generating heat.

You can shore it up however you like. Some people use plywood or foam board or plexiglass.

Scaffolding to install AC?

Found the bureaucrat!

Is this actually illegal in many places? I proposed this to my parents in Germany and they seemed to be under the impression that they could install one but their village is getting a village-wide heat pump system this fall that can also cool in summer, so they are just sitting this summer out as is.

I highly doubt there are many (if any) places with "installing any kind of AC is illegal" laws.

On the other hand, there are plenty of noise-related laws preventing you from installing an AC loud enough to be a nuisance for your neighbors. But that's solved by getting one with proper sound isolation, or placing it in such a way that the noise doesn't travel to the neighboring properties.

Similarly, you aren't allowed to install an AC on the facade of a protected historical building. But that can be solved by installing it on the rear of the building (where it is invisible), or by placing the unit itself indoors and using hidden air vents.

There's also the issue of landlords and HoAs banning you from making modifications, but that's not really a matter of legality.

The rules in NL at least are 45dB during hte day, 40dB at night, at property line.

Our machine in "silent" mode is around 42dB, and we can get it to 40dB with a little distnace from property line and a sound barrier between it and the neighbour. It really is _shockingly_ quiet compared to the dull roar of AC that was ubiquitous to me growing up in central California. (40 dB is "faint" or "computer/babbling brook according to https://soundproofingguide.com/decibels-level-comparison-cha... ) Neighbours still whine about it though. I think they dislike A/C on principle, though.

In plenty of rental accomodation you are not even allowed to put a nail in the wall to hang a picture from.

I don't think forbidding that is legal in Germany

Its not.

But making a hole in the wall to the outside is. That would generally be considered a permanent change and requires approval from landlord and in case the apartment building has multiple owners, approval from those as well

Grumpy old German and Dutch boomers whine if the AC isn’t literally inaudible. Modern ones are very quiet but will still get complaints.

Not an engineering problem, but installing a good (not the mobile AC with the flimsy fabric window seal) AC is not easy in a lot of cases. You need the OK from your landlord and since you mount something on the exterior you also need the OK of many neighbors.

You also need an electric wire/fuse with a certain capacity and not every house has that, esp. when it's old, they cook and heat with gas; worse if the cabling etc. up to the property has to be updated too. And this might sound trivial but if it's a block of flats and every flat installs at least one AC unit all of this adds up to huge additional demand which is far far more than a small hole.

That's for a larger unit. Most of the world is using low power mini splits that draw less than the max on one outlet. You only need to cool the bedroom(s).

Trust me, the rest of the world has figured this problem out a long time ago. The hottest countries in the global south tend to also be the countries with low electrical capacities.

If you live in a country where 3kW is the electrical capacity of your entire house, you just buy an AC that draws around 1kW.

You size the AC units to your circuit you don't size your circuit to the AC.