Window air conditioners or single room air conditioners work best when installed in the appropriate sized room. Just because an air conditioner is big does not mean it will cool a room quickly or more efficiently. In this case, bigger is not always better.

To work, the unit has to remove all the moisture from that room. The room feels cool because the moisture is removed from the air. The size of the machine matters since it determines exactly how long it will operate, and if it will work long enough to remove the moisture from the room.

Ratings for AC's are given in terms of BTU's (or British Thermal Units). BTUs measure the amount of heat being taken out of a room and the energy being put out. The heat is moving from inside the room to outside so the cooling coil inside is cool and the outside coil is hot.

Most households don't need any more than a 5000 BTU machine for a single room. What size you need depends on the size of the room you want to put it in. If the area of your room is between 100-250 sq. ft in size, then a 5000-6000 BTU unit will work fine. Similarly if the room is anywhere between 250 and 400 in size you can manage comfortably with a 6000 BTU to 8500 BTU machine. Calculate what you need based on this.

Before you decide what type of air conditioner you need and the size, you have to determine which room you will put it in. Consider where the unit will provide you with the most comfort. Most people think the bedroom is the ideal place. After a hard days work, you want to get a good nights sleep in a cool room.

Nobody said you have to install you air conditioning unit in the bedroom. You might not like the cold atmosphere while going to bed and can therefore choose to put the machine in the living room instead, where the whole family can enjoy its benefits all evening.

Wherever you ultimately put your air conditioning unit make sure your expectation from it is realistic. It is designed to cool one area, and even if you think it can, it's not make to cool more than one area. Most window AC's do not have the sort of blower to cool a couple of interconnected rooms. If you want the other rooms to be cooled too get yourself a couple of smaller units and fix them in all your rooms.