Much of the work in minimising running costs on your ducted reverse-cycle air conditioning (RCAC) system begins with selecting the right unit. The first part of this article gives some factors to consider while buying the unit. If you already have one, however, the last part will show you how to improve efficiency on the system you already have. 

System efficiency

RCAC units have two important values: Coefficient of performance (COP) and Energy Efficiency Rating (EER), which are measures of efficiency while the system is heating and cooling respectively. Go for systems with higher COP and EER values as they are more efficient, hence cheaper to run.

All air conditioning system manufacturers are required to give these values on their product brochures. However, bear in mind that these values represent standard conditions, and therefore do not include benefits that can arise from reduced fan speeds and lower air flow. Ask your distributor how the latter factors can be leveraged to improve efficiency depending on the climate of your region.

System design

Selecting the right size of air conditioner is paramount; if the system is too small it will have to work harder to give the desired effect, resulting in more wear. Similarly, larger units will use up more energy to treat more air than you need. Talk to a specialized distributor about heat loading on your system's quotation. The heat load shows the maximum load your RCAC can take.

Another design feature is zoning, which is about dividing your house into zones to be run separately depending on occupancy. In this way, you can turn off zones in your house that remain unoccupied at certain times, like the bedrooms during the day and the common areas at night. However, the air conditioning system must be designed to allow for zoning, or else you won't make any savings. Before buying, find out how many zones you can programme into your unit, and which zones can be run simultaneously, if any.

System control

Once installed, ensure you set sensible temperatures depending on your region's climate. A 1°C reduction in the thermostat temperature can result in up to 15% cost savings without significantly affecting ambient room temperatures. Also, running the systems at maximum capacity will cost more and result in more wear-and-tear over time.

On days that are forecasted to be excessively hot, you can reduce your energy consumption by pre-cooling your house the previous night. This is particularly useful for houses with high thermal mass, like brick houses. Pre-cooling allows your system to get a head-start on the heat load as the day warms up, keeping your house cool without over-exerting system components. Similarly, pre-heat the house on expected cool days.

Finally, ensure your RCAC filters are cleaned frequently to prevent clogging, which reduces system efficiency and increases the noise levels. How often you should clean out the filters depends on how dusty/windy your area is, but monthly cleaning is a good target for more dusty areas.