Guide to air-conditioners


G TIP: Keep your air-con at 23˚C or higher. Setting the air-con to run a few degrees warmer can save $110 and 11,000 black balloons of CO2 a year.

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Ducted systems

A ducted cooling system is a whole-house option, like central heating. It cools the home via ducts or vents in every room, connected by pipes to a main condenser. Ducted systems can use refrigerative, evaporative or geothermal cooling, and have high installation costs. Running costs vary according to the type of cooling system used and the best systems are zoned, so you can control which rooms or parts of the house you cool.


Before you hit the showrooms, do your homework to make sure you buy the most energy-smart model available.

Most fixed refrigerative air-conditioners have a star-rated energy label, with more efficient products getting more stars. The potential energy savings are enormous. For example, a 6-star rated cooler will use 28 per cent less energy than a 2-star equivalent, according to HEAT. See the air-con section at www.energyrating.gov.au for a full range of products and ratings.

It's also worth getting expert advice on the size of unit needed to cool your space.

"As a guide, allow 125 watts or 0.125 kW per square metre of floor space for living areas and 80 watts per square metre for bedrooms," says McQuire.


How you install and use your air-conditioner also has a big impact on its efficiency. With refrigerative systems, avoid installing the outside unit on a hotter north or west-facing wall where they'll have to work harder. You also need to ensure the room is completely sealed.

"Minimise heat loss by placing draught-stoppers on exhaust fans around door and window frames," says the ACF's Graham.

In comparison, evaporative coolers require good ventilation, so check there is a good cross-breeze through open windows and doors.

Cut down on heat getting in through large areas of glass such as the walls of bi-fold doors. Draw curtains or blinds when using an air-conditioner to stop up to 16 per cent of heat transfer through the glass.

Avoid the temptation to set your air-conditioner's thermostat to super-chilled. Setting the temperature between 25 and 27˚C in summer should be just right.

"Every degree below that will make 10 to 15 per cent difference in running costs," says Green Makeover's McQuire.

Last of all, make sure you clean your air-conditioner's filters regularly to reduce dust circulation and maximise airflow.


Refrigerative air-con uses 1,100 kWh of energy per year, and will cost $100 per year
Heat pumps 385 kWh of energy per year, and will cost $35 per year.
Evaporative air-con 220 kWh of energy per year, and will cost $20 per year.
Ceiling fan uses 20 kWh of energy per year, and will cost $2 per year.

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