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White kitchen with stainless steel appliances and overhead air conditioning unit
Kilowatts, split system, BTU rating, Grid Connect … cut through the jargon and discover how to find which air conditioner you need with our easy-to-understand buying guide.


Types of air conditioners

Portable air conditioners can be plugged straight into the mains and positioned in any room or household area where they are needed. All that is required is a nearby window or other opening where the hot exhaust air can be vented to the outdoors via a supplied hose. This is a good portable ‘plug and play’ option for people who are renting, as it is perfect for small spaces and doesn’t involve any structural modifications to the home.

Split system air conditioners are the most popular installation-type units. With the split system format, the compressor is positioned outdoors and connected by insulated pipes to the head unit inside. The air conditioner head is the component that circulates the air in the room to cool it, heat it (if it’s a reverse cycle model) or change its humidity level.

Window/wall mounted units are all-in-one appliances that are installed into a permanent opening in a wall or window. This is a simple and cost-effective option that tends to be cooling-only (see below), and is normally easier to install than a split-system unit.

Cooling only refers to air conditioners that cannot be switched to heating mode.

Reverse cycle air conditioners can be used for heating as well as cooling. In heating mode, the refrigerant (a chemical used to ‘dump’ heat from inside to outside when the appliance is in cooling mode) is used to extract heat energy from outdoors. The warmed refrigerant is then pumped through the head unit indoors, which circulates air around it and propels the warmth into the room using a fan.

What size air conditioner do I need?

There are many factors to consider when choosing the best air conditioner for your space, so the final appraisal should be made by a qualified professional. Bunnings can supply you with a measure and quote as part of the installation service it offers to customers buying a Carrier heat pump.

However, for budgeting and to narrow down your selection, it is useful to have a rough idea of what size you will need. Simplified power estimates do not take into account factors such as how well insulated the space is, ceiling height, number of north-facing windows, and so on. 

As a rule of thumb, a small room of roughly 25 square metres will require an air conditioner of about 3kW, while a larger room of 40–50 square metres will require a unit of at least 6–7kW.

Tip: To calculate the area of your room in square metres, multiply its length by its width.

Styled living room featuring an air conditioner, beige sofa, timber coffee table and console

Air conditioner running costs

How much an air conditioner will cost to cool or heat your home will depend to a large extent on its capacity in kilowatts, but the equation is not as simple as ‘more power equals more cost’. The efficiency of the unit you choose will also have a major influence, and the rating sticker on the appliance will show this, as well as its energy star rating. 

For an accurate idea of one air conditioner’s running cost compared to another, check how many kilowatt hours (kWh) it is estimated to consume per year, as listed on its rating sticker.

What does BTU mean?

You may see an air conditioner’s output listed in terms of BTU, which stands for British thermal units. This is an imperial measurement that indicates an air conditioner’s ability to change the temperature of the air in a room.

How to reduce your bills

When the weather turns cold, running your air conditioner in reverse cycle mode is an excellent energy-saving feature, as it is one of the cheapest ways to heat your home. This is because even when it is very cold outside, the unit can extract warmth from the air using less electrical power than the heat energy it produces.

Air conditioner extras

Allergen filters on most air conditioners capture and eliminate bacteria, fungal spores and dust particles from the air.

Auto-clean options on some models actually wash dirt and grime off internal components inside the head unit for you.

Wi-Fi connectivity means you can control your air conditioner via a smart home system such as Grid Connect, Amazon Alexa or Google Home, and use your smartphone as the remote control.

Timer functions and sleep mode are popular features that let you set when the air conditioner turns itself on, and switches it to a low-power mode while you sleep.

Long reach or long distance airflow on more powerful air conditioners propels cool or warm air up to 18m into an indoor space. This gives you effective temperature control even in very large open-plan areas.

Close up of a person's hand remote-controlling the thermostat of a smart air-conditioner in a living room

More tips for keeping cool this summer ...

Check out these five ways to reduce your cooling bills, and the wide range of air conditioners available at your local Bunnings.


Photo credit: Getty Images


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Health & Safety

Asbestos, lead-based paints and copper chromium arsenic (CCA) treated timber are health hazards you need to look out for when renovating older homes. These substances can easily be disturbed when renovating and exposure to them can cause a range of life-threatening diseases and conditions including cancer. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer or visit our Health & Safety page.

When following our advice in our D.I.Y. videos, make sure you use all equipment, including PPE, safely by following the manufacturer’s instructions. Check that the equipment is suitable for the task and that PPE fits properly. If you are unsure, hire an expert to do the job or talk to a Bunnings Team Member.