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What Is The Cost Of Running Ducted Air Conditioning?

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What Is The Cost Of Running Ducted Air Conditioning?


With Australia’s extreme temperatures, many homeowners switch on their air conditioning without hesitation to keep their home at a comfortable temperature. But with heating and cooling costs accounting for around 40% of an average Australian household’s energy bill, the costs can add up. Ducted systems are known for being highly effective and energy-efficient, but how much does it cost to run ducted air conditioning?

What affects ducted air conditioning running costs?

The cost to run ducted air conditioning depends on a variety of factors including:

  • The size and type of your system
  • The energy efficiency of your system
  • The thermostat temperature you choose
  • What time/s you operate the system and for how long
  • What your house is constructed of and how many storeys it has
  • The height of your ceilings and the size and orientation of the rooms
  • Whether your home is insulated, and the quality of insulation

How much do ducted systems cost to run?

This depends on the factors mentioned above, as well as your electricity provider and tariff structure. According to a survey done by Canstar Blue, an average household can pay between $300 and $600 in electricity costs annually. This mirrors a recent review completed by Choice magazine that analysed costs by system capacity/electricity usage, with the results showing:

        Size Annual cost to run
Small – up to 4kW $306 to $492
Medium – 4-6kW $391 to $552
Large – over 6kW $286 to $586

 

But how do you measure usage? Here’s an example that may make it a little easier. It is based on cooling a standard household that:

  • Has a 20kW ducted air conditioner with six zones
  • Has an average air conditioning output of 6kW
  • Has a system that is used for 80 hours per quarter
  • Pays 24 cents per kWh in electricity usage

While the maximum output on this ducted unit is 20kW, a correctly sized unit shouldn’t need to work at its full capacity to cool a home. Therefore, you can assume the unit is only cooling intermittently at an average capacity of around 6kW. Assuming a modest usage of around 80 hours per quarter, the system uses 480kW of electricity a quarter. If the usage rate is 24 cents per kWh, it is adding $115.20 to the household’s quarterly electricity bill, which is more than $450 a year.

How can I calculate my air conditioner’s energy efficiency?

An easy way to calculate the efficiency of a ducted system is by using its star rating label. But unfortunately, unlike window and split systems, ducted systems don’t have to carry the energy rating label. If your unit does have one, here’s how to calculate the cost to run it:

  1. Look for the printed label on the side of the unit and note the electrical consumption (total input per kWh) at its rated capacity of the air conditioning. 
  2. Multiply this power input by the kilowatt-hour (kWh) cost that will be listed in cents on your last electricity bill. This is the cost per hour to run your ducted air conditioning system. 
  3. Calculate the daily cost to run the unit by working how long the air conditioner will run and at what capacity. For example, if your electricity costs 20 cents per kWh and your unit has a total input of 3kW at full rated capacity, then the cost per hour is 60 cents. If you run the unit at 50% capacity, it would be 30 cents per hour. Keep in mind though, different rates may be charged for electricity at different times of the day due to peak rate times. If this is the case, you may need to do multiple calculations.

How can my ducted system work “smarter”?

Many ducted air conditioning suppliers integrate Smart technologies into their installs, which can enhance efficiency and reduce power bills. Depending on the brand, they offer:

  • The ability to control multiple zones, enabling you to set the exact temperature and airflow of each area or room from one conveniently located hub.
  • Automation features allowing you to only heat or cool the areas you want when you need them or when they are being used. 
  • Individual Temperature Control (ITC) sensors that detect temperature differences between rooms depending on their orientation. 
  • Integration with apps or voice-connected devices like Google Home that can control and monitor your ducted air conditioner remotely. 
  • Energy-saving motion sensors that adjust the target temperature when rooms have been detected as empty for a certain period. 

How can I reduce my air conditioning bills?

If you’re considering installing a ducted system 

  • Consider a system that includes zoning to control the extent of the heating and cooling, and enables you to turn it off in unoccupied areas. 
  • Ensure it is the correct size for your home — most energy-efficient houses these days meet the requirements of the Building Code of Australia (BCA), so they require less heating/cooling and smaller capacity systems to do the job. 
  • Your installer should make sure the ducts are the correct size and have adjustable outlets (also called registers). Ducts also need to be larger if the system will be used for both heating and cooling.
  • If your system is reverse cycle and can provide heat, floor outlets are often better than ceiling outlets, as warm air naturally rises. The outlets will therefore be able to deliver heat where it is most needed.
  • Ceiling outlets can still work well, but only if rooms are adequately sealed from draughts. This is because if cold air enters from externally facing doors, it can form a layer above the floor. The less-dense warm air from the ceiling vents is then stopped from heating the air near the floor, creating a “warm-head-cold-feet” effect.
  • Your installer should also ensure there is a return air path from every outlet back to the central system. Without this, warm air can escape and the system can suck in cold air. This will dramatically reduce its effectiveness. A gap under the door of each room that has a duct outlet installed, will create a return path between the room and the central return air inlet.

If you already have a ducted system

Although electricity costs and power input determine the cost of running ducted air conditioning, there are a number of things you can do to reduce your power bills, including:

  • Adjusting the thermostat: The easiest way to reduce the impact on your electricity bill is by maintaining a consistent temperature throughout the day. Costs can increase by 10 to 15 per cent for each degree lower you set your system (to cool in summer) and higher (to warm in winter). For maximum energy efficiency, it’s recommended you set the temperature to around 24°C in summer and 19°C in winter.
  • Insulating your home: Insulation will not only help to retain cool air in summer, it will make your home easier to warm in winter. The most economical time to install insulation products is during a home’s construction, however ceilings and suspended floors that are easy to access are relatively simple to insulate post-construction.
  • Taking note of the timing: When a hot day is expected, turn your air conditioner on early rather than waiting until the hottest part of the day (and vice-versa in winter). This will reduce your system’s running costs because it will take less energy to maintain the temperature of a cool room than it will to cool down a room that’s already hot.
  • Getting in the zone: The zoning features on air conditioners can also considerably reduce running costs. You can choose which zones or rooms in the house to cool or heat based on what areas are in use, rather than heating/cooling the entire house. If you choose a system with inverter technology, it will also continually adjust the heating and cooling output according to a room’s temperature, and keep it constantly maintained and running more efficiently.
  • Closing windows and doors: While your system is running, close all external doors and windows, and shade windows with blinds or curtains during particularly hot days (to keep the heat out) and cold nights (to keep the heat in). Double-glazed doors and windows can also help reduce the amount of heat entering your home compared to standard glass.
  • Throwing some shade: In summer, it can be tempting to take advantage of breezes and air conditioning at the same time, but it can decrease your system’s effectiveness. To reduce heat absorption and maximise your unit’s effectiveness, turn off any lights not in use and close off the room/s you are cooling to trap the air. You should also consider shading your home — with louvres, pergolas, deep verandahs and trees to keep it out of direct sunlight.
  • Maintaining it regularly: Ensuring that your air conditioner is regularly serviced is probably the most effective way to reduce running costs. This includes engaging a licensed professional to clean and replace filters and coils and make any preventative repairs to maximise its life and keep your home comfortably cool and warm year after year.

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