Ducted Heating Replacement Cost in Melbourne (2026 Guide)

A gas ducted system is four separate things, and only one of them usually fails. There is the furnace itself, which sits in the roof space or under the floor and contains the burner, the heat exchanger and the fan. There is the ductwork that carries warm air around the house. There are the outlets and the return air grille. And there is the controller on the wall.

When a heater is condemned it is almost always the furnace, and most often the heat exchanger. That is the component that separates combustion products from the air you breathe, and once it cracks the unit cannot be repaired and returned to service. A technician who condemns a heat exchanger is not upselling you, they are doing the only thing available to them.

So the practical question at replacement time is not what a new heater costs. It is how much of the rest of the system can stay. We assess all four parts before quoting any ducted heating replacement, because the answer changes the number by several thousand dollars.

This is the decision that sets the budget, and it is worth making deliberately rather than defaulting to whatever is already there.

A like for like gas replacement is the cheapest way to get heat back. The new furnace lands roughly where the old one sat, the existing ducts and outlets are reconnected, the gas and the flue are reworked to suit the new unit, and the electrical connection is made off the existing supply. Indicatively that is $4,000 to $7,500 for a typical Melbourne home where the ductwork survives, with capacity, star rating and access setting where in the range you fall.

Changing over to ducted reverse cycle costs more up front and less to run. There is an outdoor condenser to site and mount, an indoor fan coil in the roof space, a refrigerant pipe run between them, a new controller and a substantially larger electrical connection. Indicatively that is $9,000 to $16,000 on single phase for a typical home. The running cost difference is the offset: reverse cycle delivers roughly 3 to 4 units of heat per unit of electricity, while gas converts roughly 80 to 92 percent of its fuel into heat, which works out at 28 to 36 cents an hour against 50 to 72 cents for ducted gas and saves most households $200 to $450 a year. The gas ducted versus reverse cycle comparison works through that trade in detail.

There is a third option people forget. If the house is only really heated in two or three rooms, a whole ducted system may be more than the household needs. Two or three split systems can cover the lived in areas for less than a ducted changeover and give you cooling in the same units. Worth pricing before committing to ducted out of habit.

Sometimes, and this is the single largest swing factor in a ducted quote. Flexible duct has a service life. Insulation compresses, the inner core tears, joins pull apart at the take offs, and rodents in a Melbourne roof space do the rest. Duct that has been walked on by three decades of trades is rarely in the condition it left the factory in.

For a gas to gas replacement, sound duct can usually be reconnected to the new furnace, which is why the like for like number is what it is. Duct that has failed is replaced at an indicative $1,500 to $4,000 depending on how many outlets there are and how bad the roof access is, and that cost sits on top of the furnace.

For a changeover to reverse cycle the answer is more nuanced. Ducted gas systems deliver a smaller volume of hot air, while reverse cycle moves a larger volume at a lower temperature. Ducting sized for gas is often undersized for a reverse cycle system, and undersized ducting shows up as noise at the outlets and rooms that never reach temperature. Some existing ductwork can be reused, some can be reused with the main trunk upsized, and some has to go entirely. Anyone who tells you over the phone that your ducts will definitely be fine has not looked in your roof.

Outlets and grilles are the easier part. Floor and ceiling outlets can usually be reused if they are intact, though a reverse cycle changeover often wants a larger return air grille than gas needed, an indicative $300 to $600 addition.

These are indicative ranges for Melbourne homes with reasonable roof or subfloor access. They are a planning guide, not a price. A written quote after a site inspection replaces every one of them, because ductwork condition and access are things that have to be seen.

Two houses in the same street can produce ducted quotes several thousand dollars apart. These are the reasons, and all of them are visible to someone who has been in your roof space.

Victorian Energy Upgrades can apply when you replace gas heating with efficient electric heating, and it is a discount applied directly to your invoice rather than something you claim afterwards. There is no income test, but the property must be at least two years old and there is a minimum customer contribution of $200 including GST. The program changed on 30 September 2026, so the amount has to be confirmed in writing at quote time.

On running costs, the arithmetic is straightforward. Reverse cycle moves heat rather than making it, which is why it returns 3 to 4 units of heat per unit of electricity while a gas burner is capped by the energy content of the fuel it burns. In practice that is 28 to 36 cents an hour against 50 to 72 cents, and $200 to $450 a year for most households. If the changeover also lets you disconnect gas entirely, the daily supply charge comes off on top of that.

The honest version of the payback conversation is that a gas to gas replacement is cheaper today and more expensive every year afterwards, while a changeover is the reverse. If your furnace has failed in July and the budget is what it is, replacing gas with gas is reasonable and we will do it properly. If you are planning ahead, the changeover case is stronger. The winter heating bills guide covers the savings that sit alongside the equipment choice.

Ducted quotes are hard to compare because two documents can describe visibly different work in almost identical words. Ask every contractor for the same four things.

First, the capacity and model of the unit being supplied, not just the brand. Second, an explicit statement about the ductwork: reused as is, partly replaced, or fully replaced, and how many outlets are included. Third, what the electrical scope covers, including whether a dedicated circuit or a switchboard upgrade is priced or assumed unnecessary. Fourth, on a reverse cycle changeover, where the outdoor unit is going and how long the pipe run is.

Then check the licensing. Refrigerant work requires an ARC licence and the electrical connection requires a licensed electrician who issues a Certificate of Electrical Safety. A quote that is silent on both is not cheaper, it is incomplete. Pivot Trade Services holds REC 37223 and SAA accreditation S3962281, works across Melbourne western suburbs from our Altona workshop, and every installation carries a 12 month workmanship guarantee on top of the manufacturer warranty. If you want the ductwork looked at before you commit to anything, get in touch and we will go up there.