Two very different ways to heat a house
Ducted heating warms the whole home through vents fed by a central unit, and in Australia that unit is usually either a gas furnace or an electric reverse-cycle (heat pump) system. They feel similar from the vent, but their running costs work in completely different ways because one burns fuel and the other moves heat.
A gas ducted furnace turns most of the gas it burns into warm air — a modern condensing unit is quite efficient, an older one much less so. You pay for gas in megajoules, plus a daily supply charge for the connection. An electric reverse-cycle ducted system is a heat pump: for each unit of electricity it draws, it delivers roughly three units of heat, which is why its running cost can undercut gas even though electricity costs more per unit of energy.
Comparing the running cost fairly
The fair comparison is cost per unit of useful heat delivered into the house, not the sticker rate of each fuel. Gas might look cheap per megajoule, but a furnace loses some of that energy up the flue, while a heat pump multiplies each kilowatt-hour of electricity into several times as much warmth. For many homes those two effects roughly cancel out, and the winner depends on local rates and the age of the equipment.
As a rough guide, an efficient reverse-cycle ducted system delivering heat with a coefficient of performance around 3 draws maybe 2 to 4 kW to heat a house, or around 70 cents to $1.40 an hour at 35c/kWh. Gas ducted heating for the same house often lands in a similar or slightly higher hourly range once you include the daily supply charge, though older gas furnaces and cheap gas rates can shift it either way.
The honest answer is that there is no universal winner. If you already own working gas ducted heating, the running-cost saving from switching to electric has to pay back a big installation cost. If you are replacing an old system anyway, an efficient reverse-cycle system is usually the cheaper long-term choice, and it doubles as summer cooling.
Seasonal and regional notes
Heat pumps lose some efficiency in very cold weather because there is less heat in the outside air to move, so in an alpine or frosty inland climate a gas furnace can close the gap on the coldest mornings. In milder coastal climates the heat pump keeps its efficiency advantage almost year round.
Gas ducted heating dominates the winter quarter of the bill in cold-climate cities like Melbourne, Canberra and Hobart. A home that runs it hard can use several times more gas in July than in a mild month, which is why the winter bill can be a shock even when the annual average looks reasonable. Watching that seasonal spike is the key to keeping it in check.
How to cut ducted heating costs
- Zone the system so you only heat rooms in use rather than the whole house — this is the single biggest saving on ducted heating.
- Set the thermostat around 18-20°C; every degree higher meaningfully increases fuel or electricity use.
- Seal draughts and close doors to unheated zones so warm air is not leaking away.
- Use a timer so the house is warm for waking and evenings, not heating an empty home all day.
- If you run an electric reverse-cycle system and have a time-of-use tariff, pre-heat late in the off-peak window rather than during the evening peak.
- Service the unit before winter — a clean filter and tuned burner or coil keep it running at rated efficiency.
Where EnergySorted fits
Whether you heat with gas or electricity, the running cost is the usage multiplied by your rate, and the rate is the part you can change today. EnergySorted compares your real usage across more than 16,000 electricity and gas plans without taking retailer commissions, so the ranking reflects what you would actually pay through a cold winter rather than a marketing figure.
If you are weighing up a switch from gas to electric heating, the comparison also helps you see the electricity side clearly — including whether an off-peak or time-of-use plan suits a heat pump you run on a timer. The Bill Health Score then keeps an eye on whether your plan stays competitive as retailers quietly move you off introductory rates.