A high ducted heating gas bill usually traces to an inefficient or ageing unit, a high thermostat setting, heating rooms you don’t use, or a system that needs servicing. Here’s what drives it and how to bring it down.
7 min read FreshDuct Melbourne Melbourne, Victoria
A high ducted heating gas bill usually traces to an inefficient or ageing unit, a high thermostat setting, heating rooms you don’t use, or a system that needs servicing. Here’s what drives it and how to bring it down.
Efficiency FirstOld units use far more gas
Set & ZoneThermostat and zoning matter
MaintainA neglected unit costs more
A high ducted heating gas bill usually comes down to an inefficient or ageing unit, a high thermostat setting, heating rooms you’re not using, or a neglected system working harder than it should. Each is addressable.
Why Is My Gas Bill High?
A high ducted heating gas bill almost always comes down to a few factors working together: how efficient your heating unit is, how high you set the thermostat, whether you’re heating rooms you’re not using, and how well the system is maintained. The good news is that each of these is something you can act on. Understanding which is driving your bill is the first step to reducing it (see the factors above).
Unit Efficiency & Age
The biggest fixed factor is the unit’s efficiency. Gas heaters carry energy-efficiency star ratings, and older units often rate far lower than modern ones — meaning they burn substantially more gas for the same warmth. If your heater is old and your bills are high, inefficiency is part of the story. A service keeps an old unit running as well as it can, but a genuinely inefficient unit has a cost floor that only replacement or electrification lowers. See our electrification library.
Thermostat and Zoning
How you run the system matters as much as the unit. Every degree higher on the thermostat increases gas use, so a sensible setting (around 18–20°C) versus a high one makes a real difference. Zoning — heating only the rooms you’re using rather than the whole house — is one of the biggest savings ducted heating offers. Heating empty rooms is simply burning gas for nothing. See our zones guide.
Servicing and Airflow
A neglected system costs more to run. A dirty filter and poor airflow make the heater work harder to push warm air through the home, and a unit that’s overdue for service runs less efficiently. Keeping the filter clean and the system serviced ensures it delivers heat as efficiently as it’s able to. It’s a small cost that protects against wasted gas. See our running costs guide.
How to Cut the Bill
To bring the bill down: set the thermostat to a sensible temperature and avoid pushing it higher; zone the system to heat only the rooms in use; keep the filter clean and the system serviced; and seal draughts and improve insulation so the heat you pay for stays in. For an old, inefficient unit, the largest saving comes from upgrading to a high-efficiency unit or electrifying to reverse cycle — worth comparing if your bills are consistently high. See our reverse cycle library.
Frequently Asked Questions
Why is my ducted heating gas bill so high?
Usually one or more of: an inefficient or ageing heating unit (older units have much lower star ratings and burn far more gas for the same warmth); a high thermostat setting (each extra degree increases gas use); heating the whole house including unused rooms instead of zoning; and a neglected system with poor airflow or a dirty unit working harder than it should. Each of these is addressable to bring the bill down.
Does the age of my ducted heater affect the gas bill?
Significantly. Older gas ducted heaters often have much lower energy-efficiency star ratings than modern units, meaning they burn considerably more gas to deliver the same heat. If your unit is old and your bills are high, a portion of that cost is simply inefficiency. While a service helps an old unit run as well as it can, at some point a modern high-efficiency unit (or electrification to reverse cycle) is the bigger saving.
How can I reduce my ducted heating gas bill?
Set the thermostat to a sensible temperature (around 18–20°C) rather than higher; use zoning to heat only the rooms you’re using; keep the filter clean and the system serviced so it runs efficiently; seal draughts and improve insulation so heat isn’t lost; and run the system in steady, sensible patterns rather than blasting it. For an old, inefficient unit, upgrading is the larger lever.
Does turning the thermostat down really save much?
Yes — each degree lower on the thermostat noticeably reduces gas use, because the heater works less to maintain a lower target. Dropping from a high setting to around 18–20°C, while staying comfortable with appropriate clothing, can make a real difference over a winter. Combined with zoning (not heating unused rooms), thermostat discipline is one of the easiest ways to cut the bill.
Is ducted gas heating cheaper than reverse cycle?
It depends on gas and electricity prices and the efficiency of each system. Modern reverse-cycle (electric) heating is very efficient and, with rising gas prices and electrification incentives, is increasingly competitive or cheaper to run than gas ducted heating for many Melbourne homes. If your gas bills are high and your unit is old, it’s worth comparing — see our electrification and reverse cycle guides.
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