Many people buy an air conditioner that is too powerful, thinking it will provide better cooling. But an over-sized system is actually less effective — and wastes energy! Air conditioners remove both heat and humidity from the air. If the unit is too powerful, it will cool the room quickly but only remove some of the humidity, leaving the room with a damp, clammy feeling. A properly-sized unit will remove humidity more effectively as it cools.
The correct specification is generally allied to the size of room. The Penguin website has a table which allows you to estimate this for yourself. Sometimes, however, other factors need considering, such as if a room is particularly sunny or shady; or if the room has unusually high ceilings or a mezzanine level. For these reasons, and to assess the optimum positioning, configuration of system and the pipework involved, it's always wise to arrange a site-visit from your installer.