There are two distinct types of air conditioner, the refrigerative kind and the evaporative kind. In the humid conditions experienced in the coastal regions of Eastern Australia the refrigerative air conditioner is the more suitable. A refrigerative air conditioner consists of two coils (each similar to a car's radiator), one inside the house and the other outside. These are connected by pipes filled with a refrigerant which, through the process of conversion from a liquid to a gas, enables the air conditioner to absorb and expel heat. The refrigerant is pumped around the circuit by a compressor, transferring heat from one location to another. This is why air conditioners are also called 'heat pumps'.

Some units are only used for cooling, others have the capability of reversing the directions of the refrigerant flow and can be used for heating. These are known as "reverse cycle" units.

Reverse Cycle Air - Conditioning

The reverse cycle air conditioner is an appliance which not only pumps unwanted heat out of the house in summer, but can be reversed to pump heat into the house in winter. Thus, it can cool or heat an area as required. The heat transfer cycle of the air conditioner may be either manually or automatically reversed.

During the cooling cycle, if the air is cooled below dew point, the humidity is reduced, thus increasing the degree of comfort. In both cases the internal air is constantly filtered, and in most units the room temperature may be thermostatically controlled to achieve desired comfort conditions.

Reverse cycle air conditioners are available in various forms. Although they are slightly more expensive than air conditioners which cool only, they provide the benefit of all-year round usefulness.

Heating with a reverse cycle air conditioner is much more efficient than electric resistance heating, for example an electric radiator or fan heater.

Heat pump air conditioners do not generate heat directly from the electricity, as do the resistance heaters, but simply transfer heat from one location to another. In an air conditioner the electricity is used only to drive the heat pump cycle and circulation fan.

On an average winter's day, 1,000 Watts of electrical power can pump 2,500 Watts of heat from the outside air to the room inside. This ratio of output heating power to input electrical power (2,500W/1,OOOW = 2.5) is known as the "Coefficient of Performance" or CoP.

On warm days the CoP might be as high as 2.8, but on very cold days it drops until it is only around 1.0.

Because heating with air conditioners is so much more efficient than electric resistance heating, it is also one of the lowest cost electric heating options.