Window AC / August 27, 2018 / Francoise Salmons
The answer is It depends on the wall thickness. Sleeve specifications for some window air conditioner manufacturers include the maximum wall thickness before it will cover part of the louvers. For example Amanas 18000 BTU models have a max of 8.5 inches. If the wall thickness is at or below that these models can be used in as a wall air conditioner without adversely affecting function. So whats the problem if the wall covers a little of the louvers? Two things: 1) restriction of air movement and therefore reduced efficiency and 2) these units pull air in very powerfully. Cut wall edges could become loose allowing material to be sucked into the unit and potentially causing damage.
Side panels fill the gaps on the sides. These are also very thin so most of the sleeve is uncovered and outside. This allows for placement of ventilation louvers on the sides and top allowing free movement of air. This is the primary difference between the two types. The wide availability of louver space allows the unit to move a lot of air and this means window units can be quite powerful up to 3 tons or 36000 BTU. So window A/Cs can be effective for very large rooms. In contrast a wall air conditioner sleeve is designed for a hole through the wall. Walls vary substantially in thickness.
Another huge improvement in window air conditioners is in their appearance. Older models did not blend in very well with their surroundings. They were usually some shade of brown and looked like there was a box in your window. Window air conditioners today are much less obtrusive and look less like boxes. Corners are rounded and colors are much lighter. This gives them a much sleeker look. As with most things once they have been around for awhile cost become more reasonable and less of an obstacle. A window air conditioner can be purchase for less than two hundred dollars and often not much more than one hundred dollars. Of course this is for smaller units. Costs go up as the cooling capacity of the unit increases.