What is your air con temperature costing you?

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What temperature do you run your air conditioner? Most of you reading this probably set it around the mid-twenty degree mark in summer and high teens in winter – but how much is that costing you, and can small changes to your air conditioning habits actually save you money?

In this article, Canstar Blue looks at the ideal heating and cooling temperatures for your home, as well as how much this could possibly be adding to your electricity bill.

What temperature should you set your air conditioner?

remote-for-air-conA standard air conditioner’s temperature should be set to 25 to 27 degrees for cooling in summer, and around 18 to 20 degrees for heating in winter. This is to ensure maximum energy efficiency from your unit. Keep in mind that these temperatures assume you live in a moderate climate, but as we all know, Australia is a land of many climates.

Using average temperature figures, the below table provides a general indication of what temperature your air con should be set to in summer and winter depending on your location.

Optimum temperatures for air conditioning

Location Summer (cooling) air con temp Winter (heating) air con temp
Nth QLD, Nth WA, NT & Central Australia 21 – 23° 17°
SE QLD & NE NSW. 25° 18°
SA 24° – 25° 19° – 20°
TAS 28° 21°
SW WA 23° – 24° 18°
SE NSW, NE VIC & ACT 26° – 27° 20°
Sth VIC 24° 20°

What the above table essentially suggests is that air conditioners will have to work harder to offset harsher climates. Those living in warmer climates should set their air con cooling temperatures a little lower, while those living in cooler climates should set their air con’s heater a little warmer.

How do temperature settings affect air con costs?

The harder your air conditioner has to work, the more electricity it will consume. That means the lower you set the temperature when cooling and the higher you set it when heating, the more you’re adding to your power bill.

It is difficult to pin point how much your air conditioner temperature is contributing to your air con’s electricity usage cost, however Ergon Energy estimates that every one degree cooler in summer adds around 10% to the amount of electricity that the air conditioner uses. Using the Ergon air con cost calculator, you can see how small changes to the cooling temperature can make a considerable difference to the cost of using an air conditioner

Hourly cost of air con cooling temperature settings

Cooling capacity 21° 22° 23° 24° 25°
2.5kW $0.15 $0.14 $0.12 $0.11 $0.10
3.5kW $0.25 $0.23 $0.20 $0.18 $0.17
5.0kW $0.38 $0.35 $0.31 $0.29 $0.27
6.0kW $0.47 $0.43 $0.38 $0.35 $0.31
7.1kW $0.55 $0.51 $0.45 $0.41 $0.38
8.0kW $0.63 $0.58 $0.51 $0.47 $0.44
10kW $0.83 $0.76 $0.67 $0.62 $0.57
14kW $1.27 $1.16 $1.03 $0.95 $0.88

Assumes 27.071c/kWh electricity usage rate.

The difference in hourly air con running costs across various temperatures might look relatively minor, but it can certainly add up. Take the following illustration.

Case example:

krystal-clear-case-exampleKrystal can’t stand summer, she much prefers the cold. Krystal uses her 6kW cooling capacity air conditioner every evening for 5 hours throughout the summer months. Her air con temperature is always set to 21°.
 
Using the earlier table, we see Krystal’s air conditioner usage will cost her 47c an hour, or close to $2.35 per day. If she leaves her air con running like this for 90 days of summer, it will cost her $211.50 on her next quarterly bill for air conditioning alone.
 
Now, if Krystal instead set her air conditioner’s temperature to 24°, that would cost her 12c less per hour (35c). Her air conditioner usage would now only cost $157.50 over summer – a saving of $54!

What is the right sized air conditioner for your home?

An air conditioner should generally have at least 80 watts of output per square meter of room you intend for it to cool or heat. If a room is larger than the air con was designed to cater for, then it will be less effective at controlling the temperature – while your remote might say the air con is set to cool to 24°, the room temperature might actually be 28°. Conversely, if your room is too small for the air conditioner, the air con will over shoot the temperature you intended to set it to. Below is approximate guide to ideal air con capacities given the room size.

Room Size m^2 Cooling capacity (C) / Heating Capacity (H)
3.0m x 3.0m = 9m2 2.5KW(C)/3.2KW(H)
5.0m x 5.0m = 25m2 3.5kw(C)/3.7KW – 4.3KW (H)
5.5m x 5.5m = 30m2 3.5kw(c)/3.7KW(H) – 5.0KW(C)/6.0KW(H)
6.3m x 6.3m = 40m2 5.0KW(C)/6.0KW(H) – 6.0KW(C)/7.2KW(H)
6.7m x 6.7m = 45m2 6.0KW(C)/7.2KW(H) – 7.1KW(C)/8.0KW(H)
7.1m x 7.1m = 50m2 7.1KW(C)/8.0KW(H) – 8.0KW(C)/9.0KW(H)
7.7m x 7.7m = 55m2 8.0KW(C)/9.0KW(H) – 9.2KW(C)/10.0KW(H)

General guide only. Source: Harvey Norman

Also keep in mind the ceiling height of the area you’re looking to heat/cool. The higher the ceiling, the more powerful of an air conditioner you will need. If you’re unsure about what size air conditioner you need, seek a professional quote.

Other things to consider:

  • Sealing and insulation: If the space you’re trying to heat or cool is poorly sealed or insulated, your air conditioner will have to work harder to reach the temperature you have set (i.e. if you’re trying to cool your home down to 24°, you may have to set your air conditioner’s temperature to 20°). As we’ve seen, this can be costly.
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  • Energy efficiency: It almost goes without saying that you should try purchase an energy efficient air conditioner. An air conditioner will have a label with two star ratings. The blue one represents its cooling efficiency rating, while the orange one is for heating efficiency. In another article, Canstar Blue shows how much an energy efficient air conditioner might save you.
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  • Alternatives to air conditioning: While we have shown that using an air conditioner on lower settings can save you money, not using the air conditioner at all will save you more. Ceiling fans and pedestal fans have considerably lower running costs than air conditioners. Also consider if solar air conditioning could be right for you.

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