How to work out gas heater running costs
Cost per hour = input rating (MJ/h) × gas rate (c/MJ). A heater rated at 25 MJ/h running at full output on a 4.16c per MJ rate costs about 104.10c an hour.
| Input rating | Typical use | Melbourne (Multinet) | Canberra |
|---|---|---|---|
| 25 MJ/h | Space heater, one or two rooms | 104.10c | 141.07c |
| 50 MJ/h | Large space heater | 208.20c | 282.15c |
| 90 MJ/h | Ducted heating, whole house | 374.76c | 507.87c |
Ducted gas heating
Ducted systems heat the whole house, so they use the most gas. Zoning, so you only heat rooms in use, and a thermostat set between 18°C and 21°C make the biggest difference. Ducts in an uninsulated roof space lose heat before it reaches the rooms.
Compare with reverse cycle
A reverse-cycle air conditioner delivers several units of heat for each unit of electricity. See gas vs electric and the cheapest way to heat a home.
Gas heater safety
- Have gas heaters serviced by a licensed gasfitter as often as the manufacturer recommends.
- Unflued gas heaters release combustion products into the room. Keep the room ventilated and follow the manufacturer's instructions.
- Install a carbon monoxide alarm near gas heaters, and call 000 if you suspect carbon monoxide poisoning.
See gas leak safety.
Common questions
Multiply its input rating in MJ/h by your gas rate. A 25 MJ/h heater at full output on a typical Melbourne first-block rate of 4.16c per MJ costs about 104.10c an hour.
A ducted system rated around 90 MJ/h costs several dollars an hour at full output on typical rates. Zoning and a lower thermostat setting cut the cost.
Usually not. Efficient reverse-cycle air conditioners deliver several units of heat per unit of electricity, which makes their heat cheaper on most current prices.
Sources
Gas prices come from the AER plan data, priced by us. Heater ratings are examples; check your own heater. Last checked October 2026. Prices include GST unless we say otherwise.