I Want to Replace My Ducted Gas Heating. What Are My Options?
A plain-English guide to the main options. No sales pitch, just what's available, what's involved, and what actually matters for your home.
So your gas heating system is on the way out, or maybe your bills have finally pushed you over the edge, and you're wondering what to do about it. You've probably typed something like "replace gas heating" into a search bar and come away more confused than when you started. Heat pumps. Hydronic. Reverse cycle. It's a lot.
First, a quick thing about how gas ducting works
Your gas ducted system blows really hot air, around 60 to 70°C, through your ducts and out through vents in the floor or ceiling. It heats rooms fast, and the ducts don't need to be huge to do it.
Here's why that matters. When you switch to an electric heat pump, it produces cooler air, more like 40 to 45°C. That's still warm, but to deliver the same amount of heat into a room it needs to move more air, which means your existing ducts might not be big enough.
It isn't a dealbreaker, but it's worth checking before anyone quotes you anything.
The other thing worth doing first: your thermal envelope
Before you spend money on a new heating system, it's worth asking how much heat your home is losing in the first place. Insulation in the ceiling and walls, draught sealing around windows and doors: these reduce your heat load, which means whatever system you install can be smaller, cheaper to run, and more comfortable.
A good energy advisor will tell you this. A salesperson in a rush to quote you a system might not.
Getting an independent energy advisor, someone who isn't selling you equipment, is genuinely worth it before committing to anything. They can look at your home as a whole, insulation, solar, heating and hot water, and help you spend your money in the right order.
Your main options
Option A: a ducted heat pump system
If your ducts are old, leaky, or undersized for a heat pump, you can replace them along with the unit. New ducts sized properly for reverse cycle mean the system can perform as it should.
The upside: a clean slate, and a properly designed system that will actually deliver what it promises.
The catch: more trades, more disruption, and higher cost. If you're renovating anyway and floors or ceilings are already open, this is the moment to do it. Doing it afterwards is much more expensive.
Keeping your existing ducting. If your ducts are in reasonable condition and your home is reasonably well insulated, you might be able to keep them and simply swap the gas unit for a reverse cycle heat pump. Lowest disruption and lowest cost, but a technician needs to confirm your ducts are sized correctly for a heat pump. If they're undersized, the system will struggle on really cold days.
Option B: go hydronic, underfloor pipes or radiator panels
This one is less commonly known but worth understanding. Instead of blowing warm air through ducts, a hydronic system circulates warm water through pipes in your floor or through radiator panels on your walls. The heat radiates gently and evenly into the room.
The upside: it's the most comfortable heating money can buy. No noise, no cold draughts, no dust moving around. The heat comes from the floor or wall rather than a vent, so it feels like warmth rather than a fan heater. And there are no wall-mounted heads visible anywhere in the room.
The catch: it's a bigger job to install. You need access to run the pipes, which is why renovation time, when floors are already up, is the ideal window. If you're not renovating it can still be done, but it's more disruptive.
For cooling you would still need splits or fan coil units, because hydronic doesn't cool through radiators. Plenty of people run a hybrid setup: existing splits upstairs for bedrooms, hydronic for the main living areas.
This is what Thermal Dawn specialises in.
Option C: a VRF multi-head split system
VRF, or variable refrigerant flow, sits between individual splits and a full ducted system. A single outdoor unit connects to multiple indoor heads throughout the house. Each room gets its own head, but they all share one compressor outside.
The upside: very efficient, because the outdoor unit modulates its output to match demand across all zones at once. You get individual room control without the running costs of multiple separate compressors. Better for larger or multi-storey homes where a single ducted system would struggle to zone properly. And only one outdoor unit to worry about aesthetically.
The catch: higher upfront cost than individual splits, because you're paying for a more sophisticated system. Installation is more involved and needs a specialist. If the outdoor unit fails, all your indoor heads go down at once. Not all installers are experienced with VRF, so quality commissioning matters more here than with simpler systems.
Good fit for: larger homes with four or more rooms to condition, where you want individual zone control without visible ductwork, or multi-level homes where a ducted system would need multiple units anyway.
Option D: forget the ducting entirely, add splits throughout
The most pragmatic option. Rip out the old gas system and put reverse cycle splits in the main rooms: living area, dining room, maybe a bedroom or two. Splits are highly efficient, excellent for cooling, and easy to install.
The upside: simple, cost-effective and flexible. Each unit works independently, so you only heat the rooms you're using. Straightforward to get quotes, easy to find qualified installers, and you can stage it room by room if budget is tight.
The catch: you end up with wall-mounted heads in every room, which some people don't mind and others hate, especially mid-renovation when they want a clean finish. Multiple outdoor units add up visually and acoustically. High void spaces like stairwells are tricky for splits, because heat rises and pools at the ceiling rather than warming the room.
How to decide
It mostly comes down to three things.
- What condition are your existing ducts in? If they're in good shape and sized reasonably well, Option A is worth exploring first. If they're old and leaky, you're looking at the other options.
- Are you renovating? If floors or ceilings are already open, it changes the maths significantly. Hydronic becomes much more accessible, and replacing ductwork is far less disruptive.
- How much do aesthetics and zoning matter to you? Individual splits work fine but put a head on every wall. VRF gives you the same flexibility with one outdoor unit and potentially better efficiency at scale. Hydronic is the most invisible of all, with no heads anywhere.
A note on the cowboys
Electrification is an area where some installers take advantage. A common pattern is recommending a system far larger than the home needs, because a bigger system means a fatter margin, and you end up paying for capacity you will never use.
Get at least one independent quote. Better yet, talk to an energy advisor before you talk to anyone selling equipment. If you'd like a recommendation for someone who won't try to sell you anything, get in touch.
Want to know more about hydronic?
If you're curious about Option B, hydronic heating with thermal storage, that's what we do at Thermal Dawn. We're happy to talk through Options A, C and D too, even though we don't supply them.
Thermal Dawn builds hydronic heat pump thermal storage systems for Australian homes. We're based in Sydney and work primarily in Victoria and New South Wales.