The facts about air conditioner running costs
- Air conditioners work better at maintaining a reasonable temperature than they do at causing drastic temperature changes (such as dropping the temperature from 45C to 20C after being off all day).
- Air conditioning systems with remote controls that allow you to turn them off and on and adjust settings from a distance (like the Daikin Online Controller) are great because they allow you turn on your system before you arrive, giving it time to work efficiently towards a goal temperature.
- Regular service (including cleaning or replacing the filters) will make your air conditioner last longer and reduce the air conditioner running costs – just like your car.
- Air conditioners have limits – they’re just big heat exchangers where one side gets hot, the other cold, and the heat is dissipated into the atmosphere on cooling mode. That means outside temperature affects its performance: most modern air conditioners can handle outside temperatures up to 46C – so when a record temperature of 45.8C was set in Sydney in January, 2013, it wasn’t possible to release much heat, and many air conditioners will just turn themselves off in that situation.
- As a result, limiting the heat your home is exposed to goes a long way towards reducing your air conditioner running costs. This can include:
- Insulation, including in the roof and walls – basically anywhere you can
- Draw blinds and curtains to keep out the sun
- Add awnings to windows
- Be reasonable in your temperature expectations – a 10C-12C temperature drop can be perfectly acceptable performance
- Setting a temperature your system has no hope of maintaining will only result in huge bills. Keeping your setting in the low 20s in winter and the mid 20s in summer will keep you comfortable while keeping air conditioner running costs reasonable – there’s nothing wrong with wearing socks in the winter and shorts in the summer to stay comfortable.
- All the electrical data we’re using for this guide is accurate as of 15th January 2014. And if you’re considering ducted gas heating then have a look at our post on ducted gas heating running costs.
Air conditioner running costs, Example 1
To help put everything in context, let’s look at a couple of real world examples.
Imagine a professional couple living on the North Shore. Let’s make a few simple assumptions about them:
- It’s summer!
- They both leave for work at 7.30am, five days a week.
- They get home most nights around 8.00pm
- They have a Daikin Online Controller (love those things) and they can turn their Lounge air conditioning (a 6kW split) on about a half hour before they get home, and later on the bedroom unit (a 2.5kW split) without having to head upstairs.
- Their insulation in the roof and walls is average.
- They are on an AGL* plan with a time of use meter that splits its’ tariff into 3 sections:
- Peak – 2pm to 8pm Monday to Friday (excl. public holidays) @ 59.4 cents/kWh
- Shoulder – 7am to 2pm and 8pm to 10pm Monday to Friday and 7am to 10pm weekends and public holidays @ 25.3 cents/kWh
- Off peak – 10pm to 7am every day @ 16.5 cents/kWh
*AGL prices correct for NSW as of 25th March 2018. All AGL plan prices are the same, the difference between them is the amount of discount, etc received for duration of contract.
That’s all the information we need. What does it tell us?
When the lounge air conditioner comes on at 7.30pm via remote, it works at 100% for 15 minutes and then drops to 70% for a further 15 minutes. Then it hits the goal temperature and it runs at 40% until they go upstairs at 11.00pm.
When the bedroom unit is turned on at 10.30pm it also runs at 100% and 70% for fifteen minutes each. The temperature setting keeps the system running all night at 40%, until they turn it off at 7.00am and the whole cycle begins again.
Our calculator tool above tells us, then:
- The 6kW Lounge air conditioner is costing them $0.8446 each evening
- The 2.5kW Bedroom air conditioner is costing them $0.2931 over night
Total cost? A whopping $1.14 a day to stay cool!
Air conditioner running costs, Example 2
Maybe that $1.14 is a special case? Let’s look at another example.
This time, let’s imagine a family of four living on the Northern Beaches. Again we make some assumptions:
- Summer again, naturally.
- Dad works full time, Mum is home with the kids.
- The kids are at school from 8.30am to 4.00pm each weekday.
- They understand that it’s more efficient to keep the house at a reasonable temperature all day instead of blasting the AC when you come home.
- They have a 14kW Daikin ducted system serving the Living areas and 4 bedrooms via 8 ceiling outlets.
- They also have adequately good roof and wall insulation, and they’re on the same electric plan as Example 1.
Let’s say a heat wave hits the Northern Beaches, and Mum turns on the air conditioner at 8.30am with a temperature setting of 26C. She takes the time to close all the doors and windows and draw the blinds in order to give the system a good chance.
As a result, the system runs at 70% for 15 minutes then 40% for the rest of the day. They turn the system off at 10.30pm at night when the temperature has become a little more bearable.
Total air conditioner running costs for this 14 hour period based on our calculator: $9.24. That’s not bad for running continuously for 14 hours!
Sorry about this bit, but… Although Peninsula Air Conditioning Pty Ltd believe all the facts, figures and calculations are correct it will not accept any liability for your use of, or reliability upon, any information presented above. If your circumstances warrant it we suggest you employ the services of a suitably qualified Mechanical Engineer.