> It's a complete waste.

That's completely false. They work just fine despite not being terribly efficient at least provided you install them correctly (but that caveat naturally applies to any window unit).

In fact despite the low efficiency using only one in a single room is likely far cheaper than cooling the entire house. It's the same principle as an electric space heater versus a whole home heat pump.

Of course running a minisplit only in the one room would be substantially better but for a 1 kW unit the difference is less than $1 per day (unless you're subject to the California electric grid I guess).

They work ok in some places where have insulated windows and some source of colder air to get in.

Since these one tube systems just push hot air out, you are creating low pressure in your room and you will suck the air in from somewhere. Often times simply from outside from the leaky windows.

I don't understand why it's hard to buy systems with two hoses that would keep the pressure in the room.