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Sizing your heating system

A correctly sized heating system will ensure household warmth and energy efficiency. Systems that are too large or too small for a household’s size and demands are often inefficient, ineffective and expensive. Heaters are generally sized according to the amount of heat needed to maintain a comfortable indoor temperature on a cold winter day.

The size of a heating system should be based on:

  • room dimensions
  • insulation levels
  • window areas and coverings
  • construction materials
  • ventilation rates
  • climate and average indoor and outdoor temperatures

The tables below provide some general size and efficiency guidelines.

Your installer should carry out a heat load calculation and advise you on the correct size for your household.

If you need to heat…
Only living zones Use one or more high efficiency space heaters
Living areas for long periods,
sleeping areas for short periods
Use high efficiency space heaters for living zones and electric 'spot' heaters for sleeping areas, or a zoned central heating system
Living and sleeping areas for long periods but at different times of the day Use a zoned central heating system
Living and sleeping areas both for long periods at the same time Use a zoned central heating system
Bathrooms/ensuites Use radiant heaters, e.g. strip heaters or infrared lamps


Home Heater output required per m2 of floor area*

Energy efficient Home
Insulated ceiling and walls 80W
Insulated ceiling only 100W
Uninsulated home 130W

*For Melbourne climatic conditions. Allowances should be made for colder areas.

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