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Air Conditioning for Home Cooling

Potential Savings*
10 Year $ Savings:
10 Year CO2 Savings:
Cooling Power:
very strong – the most powerful form of cooling available
Suitable Climates:
Tropical Australia – North QLD, NT, Northern WA (cooling only). Humid coastal climates with warm summers – eg coastal NSW and south-east QLD (reverse-cycle).

Modern split-system and ducted air conditioners consist of an indoor unit and an outdoor unit. The indoor unit is what you generally see on your wall (for split systems), and contains vents that extract warm air from the home. In a nutshell, the indoor unit strips heat from the air and returns the cool air to the room. The outdoor unit takes the stripped heat and releases it outside.

Types of Air Conditioners

There are 3 main types of air-conditioning units – window/wall, split-system and ducted.

Window split and ducted air conditioning

(From left to right) Window/wall, split and ducted air conditioning units

Window/wall units

These units have the entire cooling and heating mechanism in the one box. Typically these units are installed by cutting a hole in a wall or a window, and are used to cool a single room. We’d recommend steering clear of these. Although cheaper than split systems, they are noisier, less efficient and take up more internal space.

Split system units

These units have an indoor unit and an outdoor unit which are connected by tubing that is passed through a small hole in the wall. These units can be used to cool either a single room, or an entire home (using a multi-split system unit).

Ducted units

Ducted air conditioning systems funnel air back and forth between the rooms of a house and a central indoor unit located in the roof. The air passes via a series of ducts located in the ceilings of individual rooms in your home. The indoor unit then connects to the outdoor unit via a series of pipes. Ducted air-conditioners are used to cool entire homes.

Financial and Environmental Savings

Here’s how air conditioning stacks up against a number of other cooling systems both financially and environmentally.

Cooling an Individual Room (an area of 20 m2)

Our calculations showed that using a split-system reverse cycle air conditioner was the most expensive and polluting way to cool a room. It produced around 2.3 tonnes more CO2 than a ceiling fan or a portable evaporative cooler over a 10 year lifetime (the equivalent of driving 15,800 km)1, and its total costs were about $1,000 more. Electricity alone accounted for 50% of the extra cost.

If you’re using air conditioning for cooling only (for example if you live in the tropics), your costs rise even more! You’ll end up paying close to $2,000 more over a 10 year lifetime. That’s because a cooling-only unit costs only slightly less than a reverse cycle air conditioner, but doesn’t give you the benefit of energy-efficient heating in winter. In our calculations below we’ve assumed use of an air conditioner for heating as well, so we’ve only allocated 50% of the upfront costs of air conditioning to cooling.

Ceiling Fan Portable
Air Conditioner
(reverse cycle)
Cost Installed $296 $346 $815*
Annual Energy Cost $9 $10 $64
10 Year Total Cost $387 $450 $1,450
10 Year CO2 Emissions 396 kg 454 kg 2,767 kg
Figures based on 560 hours of cooling per year and an average electricity price of 21.9c per kw/h. Air conditioning unit compared was a 2.5KW reverse cycle unit with an EER of 4.82, and portable evaporative cooler was a 14L size, capable of cooling up to 20 m2. Calculations assume 125KW of cooling per m2.

Cooling an Entire Home (an area of 100 m2)

If ducted air-conditioning is the only method you’re using to cool your home, then expect a very big bill. For a cooling-only system you’d be looking at about $12,700 extra over 10 years compared to running ceiling fans alone. Using ducted reverse cycle air conditioning brings that difference down to around $7,600 (since you save on the cost of installing separate heating in winter). Nevertheless, that’s still a lot of extra cash to be spending!

If you think the extra cost is big, then the extra CO2 emissions from air conditioning are staggering. A ducted air conditioner will emit an extra 18.4 tonnes of CO2 over 10 years – that’s the equivalent of driving a car 122,700 km!1

6 Ceiling
Air Con /
Add-On Cooling^
Cost Installed $1,776 $7,415 $5,150*
Annual Energy Cost $55 $125 $477
10 Year Total Cost $2,321 $9,208 $9,917
10 Year CO2 Emissions 2,375 kg 5,462 kg 20,776 kg
Figures based on 560 hours of cooling per year and an average electricity price of 21.9c per kw/h. Air conditioning unit compared was a 12.5KW ducted reverse cycle unit with an EER of 3.21, and evaporative cooling was a 12.6KW ducted unit. Calculations assume 125kw of cooling per m2.

Our Recommendation

Air conditioning is the costliest and highest polluting form of cooling – however it’s also the most powerful. The question you need to ask yourself is “How much cooling power do I need?” If you live in the tropics or in humid coastal parts of NSW, QLD and WA, you’ll need a lot of power, so air conditioning may be your only option. On the other hand, if you live in milder, less humid parts of the country such as Tasmania and parts of Victoria, then evaporative cooling and even ceiling fans may provide enough cooling power.

If you need to go with air conditioning, then we strongly recommend installing ceiling fans in every room as well. Running ceiling fans along with the air conditioner, or even running ceiling fans alone on milder days, could help you reduce your electricity bills to the point where the fans pay for themselves. You should also consider installing solar panels on your rooftop, as these can supply a large portion of the power you’ll need to run your air conditioner during the day.

Make sure to also check out our 10 Easy Tips for Reducing Your Air Conditioning costs.


* Represents 50% of the upfront cost of a reverse cycle air conditioner. The other 50% has been allocated to heating the room in winter.
^ Upfront costs, energy costs and CO2 emissions for add-on cooling are very similar to those for reverse cycle air conditioning, so these have been grouped together in this table.

1. Based on a car emitting 150 g of CO2 per km.

© 2018 Start Sustainable Pty Ltd.