There’s more than just the size of your room to consider when you're looking at cooling options. For example: if you live in a part of Australia with a more humid climate, evaporative cooling is more or less pointless.
Evaporative air conditioners rely on the evaporation of water to produce a cooling effect. When it’s humid and the air is already very moist, the ability of these types of coolers to evaporate water is substantially reduced, which means that the cooling effect is much less pronounced. These types of coolers can be quite effective in drier climates, but don't make much sense elsewhere.
The term 'air conditioning' isn't necessarily confined simply to cooling. It refers generally, as the name suggests, to 'conditioning' the air in your home. While we most commonly use it to refer to cooling, it can also refer to the processes of heating, ventilation and disinfection of air, as well as the process of controlling the humidity in the air.
Refrigerative air conditioners are excellent for this purpose. The evaporator coil in a refrigerative air conditioner condenses and removes the water vapour from the air, drying it out before recirculating it. Refrigerative air conditioners typically regulate indoor humidity levels at around 40-60% relative humidity. The advantages of these kinds of systems are obvious for humid climates (particularly in the north of Australia) where the ambient humidity can be much higher than this. Humidity in the air makes things feel hotter than they actually are, so the cooling effect with a refrigerative air conditioner in humid areas is very refreshing.
It's also possible to dehumidify an area without cooling it, using a dehumidifier. These systems use the same basic principle to remove humidity, but because of the energy they use (and the fact that they don't generate cool air), dedicated dehumidifiers also add heat to a room. These systems are more commonly used to protect sensitive equipment in situations where extreme humidity is a problem.
It's important to remember that there are some parts of your home that will naturally be more humid than others too. Kitchens, bathrooms and laundries all experience higher-than-average humidity levels as a result of cooking and clothes dryers. Wherever possible, it's best to avoid placing air conditioners in or near these areas so as not to unnecessarily overwork them.
Health and humidity
Controlling humidity for the sake of comfort's one thing, but it becomes counter-intuitive when the climate you create affects your health. The air that's expelled by a refrigerative air conditioner can easily irritate peoples' throats, eyes and skin if it's too dry. Likewise, studies have shown that high humidity is linked to asthma attacks, and can promote the growth of dust mites and mould. Refrigerative air conditioners help with this, not only by reducing the moisture content in the air, but also by filtering the air as it passes through the air conditioner.