Are there any window AC units that don't hang outside of the window (building requirement)? Or is a dual-hose portable AC unit my best option for an energy efficient AC unit?
Looking for 10k-12k BTU.
If they don't hang outside the window they'd have to hang inside the window, and would need a more complicated ventilation system to take air from outside, heat it up and vent it back outside. At that point you'd have a window mounted two hose AC anyway.
So yes, your next best option is going to be a two hose portable AC. One hose takes air from the outside to cool the condenser, one hose to throw that hot air outside.
Single hose works too, but they're less efficient because they take cold inside air, cool the condenser and vents it outside, which waste some of the air it just cooled for that and it creates negative air pressure inside which will bring hot air from the outside to replace it from any cracks and holes in the house.
I understand! So then given my limitation, a dual hose portable AC unit is my best option.
No question. We used a single hose one for years and it was way better than the window units in almost every sense (except for the above mentioned efficiency issue). Setup is simple, you can move/point it to a more desirable location, breakdown at the end of summer was simple, and ours was remote controlled (though this seems more common on window units too these days).
If you have a balcony or patio area (assuming you are in an apartment), you could opt for a split A/C. These have most of the A/C "guts" in a box that sits outside and a couple of hoses that hook up to the heat exchanger inside. The outside box chills water, pumping it through the inside heat exchanger. They're more efficient than window A/C units, and get around rental agreements prohibiting window units.
If the ‘window’ part isn’t a requirement. A mini-split fits the bill. They are efficient, aren’t a blight, and can be sized to service a room or so.
The whole point of window A/c is to hang outside the window so the waste/extracted heat is outside and not inside (as it would make the A/c unit useless.)
It sounds like a portable hose units your only option. (even thought they are less efficient than in window units)
Don't dual hose portable AC units follow the same principle of venting the waste heat outside? As I understand it, the window AC units are still much more efficient at this as they don't have a hose to push/pull it through.
You may be able to find a slim-profile window AC that sits within the window casing. They’re not very powerful, so plan on one in each room.