An air conditioner cools and dehumidifies the air in a room. Using a process analogous to that used in refrigerators, the air conditioner (AC) draws in warm air from the room, passes it over cooling coils, and then pumps it back into the room. The liquid inside the cooling coils warms up and is pumped to the outward-facing side of the unit, where it goes through another set of coils in contact with the outside air, transferring the room’s heat back out of the unit.
Since the cooling coil is relatively cold, the moisture from the warm room air condenses onto it, providing an additional dehumidifying effect. The air that returns to the room is therefore cooler and drier than what went in.
AC units come in a range of sizes, and choosing the right size is one important factor to consider when buying. Buy one that’s too large and it’ll be expensive to run; buy one that’s too small and it won’t do the job. Measure the size of the room before you go to buy an AC; most ACs have a chart on the side of them that tell you what size room that model is appropriate for. Of course, the larger the room, the more it’s going to cost.
More-sophisticated models will offer features such as variable fan speeds, a digital user interface, a timer setting, and an adjustable thermostat. Expect basic models to cost from around 120 USD.