The LG models LA090HSV, LSo91HSV and LW7013HR; the Pridiom AMS120HR; and the Frigidaire FRA052XT7 are some of the smallest air conditioners available. Some are window units, while others are mini-split models. A variety of manufacturers make small, portable air conditioner units.
The smallest window units are the Pridiom and Frigidaire models. The Pridiom fits in a window space 13 7/8 inches high by 18 9/16 inches wide, and it generates 7,000 BTUs cooling and 3,850 BTUs heating. The Frigidaire model is even smaller, fitting into a 12- by 16-inch slot, but it only outputs 5,000 BTUs cooling with no heating option.
The mini-split models come in two pieces. The interior air distribution unit is quite small and mounts on the wall, taking up very little space. The exterior unit is somewhat larger but is outside the house where space is not typically a major concern. Most models heat and cool and typically generate between 9,000 and 12,000 BTUs, as well as having dehumidifier options.
Portable units are generally no smaller than the smallest window units but can be located, and moved, in interior rooms as space allows. These units typically have cooling power to handle 150 to 500 square foot rooms, depending on the model.