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House & Garden

  • Written by NewsServices.com

Thinking of getting a gas ducted heating unit but you’re conflicted about a suitable size for your home? Or, you currently own a smaller one that cannot seem to heat all the rooms and you can’t help but ask, “what heater do I need?”

It’s okay. You’ve come to the right place.

When winter comes around in Melbourne, this questions always pop up. Getting a ducted heating system for your home is not a decision to be taken lightly. Especially when you are considering opting for a ducted heating unit. Knowing the right size is a key factor to consider. Here, we’ll give you a breakdown of what you need to know and do to get the right size.

  1. Measure your Home

The first thing you need to know is that the size of your home or office determines the size of your potential central ducted heating unit. And when referring to a heating system, size here is determined by power usage measured in kilowatt (KW).

Measuring your home can either be done by a professional or you can follow this procedure—Warning this may involve some math!

To start, you may need a calculator and some measuring equipment. Measure the length and breadth of each room in meters and multiply to get the area of the room. For instance, if the length of Room 1 is 10m and the breadth is 7m, that will be 10m × 7m= 70m2. Then add the area of each room to get the total area of your space. Bear in mind that ducted heating units generally circulate warm air all through the building including the ceiling. So, we must put the height of the walls into account.

Finally, measure the height of your ceiling. As a rule of thumb, the height of the ceiling determines the number of watts to be multiplied by. So;

Ceiling Height (M)

Air Con Watts Factor


multiply your total area (m2) by 150 watts


multiply your total area (m2) by 160 watts


multiply your total area (m2) by 175watts

For ceiling heights higher than 3m or lower than 2.4m, you may need to make use of some math skills. For instance, a ceiling height of 4.5m will be 4.5m × 175watts ÷ 3m= 262.5watts. In a nutshell, to calculate the size of your ducted heating unit, multiply the total room area to be heated, by the equivalent watt of your ceiling height and convert to kilowatt (by dividing by 1000).

Let’s say a home of 150m2 total area and a 2.7m ceiling height. That will be 150m2 ×160 watts= 24000watts which is 24KW. A 24KW unit will be the size for this home.

Normally, this estimate would be enough to make a decision but there are a few other factors to consider when choosing the right size of ducted heating. So, stick with us and find out.

  1. Insulation

There are calculations to determine the impact of the quality and amount of insulation on the size of the gas ducted heating system. But this physics can be quite cumbersome and may require the help of a professional. The structure of a building is made up of different insulator materials such as fiberglass, mineral wool, air crete, etc. To make a ballpark estimate, if your space is well insulated, that should raise the kilowatt by a figure or two.

  1. Number of Occupants

Heat gain per person is another factor that may contribute to the size of your ducted heating unit, albeit in a little way. The body produces heat on its own and each person emits a range of 100-500 watts. This can be very considerable if the number of home occupants increases. If your space is an office usually crawling with people, that should decrease the kilowatt by some figures.

  1. Heat Generating Appliances

This factor is commonly overlooked but it is worth considering. Appliances like light bulbs, stoves, washing machines, photocopiers, and other office appliances can contribute to heat production in homes and offices. If your space has an abundance of a heat-generating appliance, that should decrease the kilowatt by a smidgen.

  1. Number and Style of Windows and Doors

The style of windows and doors present in a home is very important. Especially in cases where the fixtures open all the way for passage of people and air such as sliding doors and windows—double-hung and casement windows. The amount of heat loss from this factor may seem negligible if there are fewer windows and doors in the home.


Several factors determine the size of a ducted heating unit, the chief of which is the size of your home. The other factors may seem less significant but are worth knowing regardless. By taking into account all these factors, you are well on your way to enjoying the coziest winter while saving money and the environment.

To find out the exact size of ducted heating you need, it’s best to speak to one of Comfyhome’s specialist, call us now on 1300 266 394.

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