Going through our list, you may have noticed that some of the small ACs have single-hose designs while others have dual-hose designs. Single-hose AC units take air from inside the space, cool it, and release most of the air back into the room. The rest of that air is used to cool the inside of the machine and the resulting hot air is then released outside through the single hose.
This means that the machine will have to constantly work to “replace” the air that was taken from the room and pushed outside. On the other hand, a dual-hose AC unit has one hose to take in air from the outside that is cooled inside the machine and released in the room and another hose through which hot air and moisture is released. This means that air conditioning is done more efficiently.
But ultimately, which one is best for you will still depend on your needs. If you have a small space, then a single-hose AC will work perfectly well. But if you have a large space, then you may find better cooling results with dual-hose portable AC units.