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Air conditioning - what to ask before you buy

If you're thinking of buying an air conditioner, but you're not sure what to ask before you buy, here are some suggestions to help you decide what air conditioner is best for you. If you want to save on running costs and the environment, check the star rating.

Click on a question below for more information.

Size: What size air conditioner do I need?
Cost: How much does the air conditioner cost to run?
Use: How long will the air conditioner run each day?
Heating: Is the air conditioner safe for heating?
Star rating: What is the star rating for the air conditioner?
Installation: What kind of air conditioning installation is best?
Noise: How noisy is the air conditioner?
Inverter: What's an inverter?
Refrigerant: What kind of refrigerant is used in the air conditioner?
Spare parts: How long will spare parts be available for the air conditioner?

1. What size air conditioner do I need?

Air conditioner outputs are measured in kilowatts (kW). A rule of thumb is to allow 125 watts, or .125kW per square metre of floor area for living rooms and around 80 watts or .080kW for bedrooms. However, this will be affected by the size of your house and whether it is energy efficient - e.g. Does the house have insulation in the ceiling and walls? Are there lots of windows to transfer heat in during summer and out during winter? Have you draught-proofed doors and windows? What equipment will be used in the rooms? Will they be inhabited 24 hours a day?

If you are installing a large and/or expensive system, ask for a detailed heating/cooling load estimate from the air conditioning manufacturer or installer to ensure you are buying the right system.

2. How much does the air conditioner cost to run?

Find out how much it costs to run, for cooling and/or heating. As electricity costs always go up, choose the system with the lowest running cost. It may be worth paying a little more for a system with lower running costs for a longer term benefit. A more efficient unit may also add better value to your home.

3. How long will the air conditioner run each day

Figure how much use it will get in summer/winter. Also, if the house is empty during the day costs will be lower.

4. Is the air conditioner safe for heating?

Find out what safety features exist when the unit is used for heating.

Reverse cycle systems are safer than other heating systems because there is no exposed heat source and they do not become dangerously hot.

5. What is the star rating for the air conditioner?

The more stars, the better. Reverse cycle systems are efficient room heaters too, so there's a rating for both heating and cooling.

6. What kind of air conditioning installation is best?

Reverse cycle systems provide heating as well as cooling. If you want both, check that the cooling and heating are both effective - some are better at cooling than heating. Reverse cycle air conditioners are the most efficient way to heat your home (up to 3 times more efficient than other heaters) and have low running costs.
Ducted systems are very convenient, but are more expensive both to install and to run, so check out other options first. Some allow different temperature selections in different rooms - check this out. If you decide on ducted, get one specifically designed for the situation. Ducted is best added when a new home is being constructed.
Split systems are less expensive than ducted systems but still involves installation.
Window installation may be preferred if you are renting premises - it may allow you to take the air conditioner when you go.
Wall installations need to have a hole made in the wall. Check the costs and practicalities of this (e.g. strata regulations for units).
Portable units are expensive, although of course they avoid the cost of installation. They tend to be less effective than built-in models, can be noisy, and produce water that has to be dealt with.

7. How noisy is the air conditioner?

Check out the noise rating. Split systems separate the compressor from the control unit so they tend to be quieter inside the house. However, some brands are quieter than others so check this out. If you're in a strata situation, the noise of the outside compressor may cause problems with neighbours.

8. What's an inverter?

This means the air conditioner has a variable speed motor driving the compressor. These work out cheaper if a system is on for long hours rather than for short periods at maximum setting, because they can vary their heating or cooling according to the conditions at the time.

9. What kind of refrigerant is used in the air conditioner?

Check if it is safe in the environment. This should be clearly stated on the unit

10. How long will spare parts be available for the air conditioner?

The usual range is 5-10 years but may be less for cheaper units.