I want to replace my ducted gas heating. What are my options?

Published by Thermal Dawn

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 Google and come away more confused than when you started. Heat pumps. Hydronic. Reverse cycle. VEU rebates. It's a lot.

This is a plain-English guide to your main options. No sales pitch, just a breakdown of what's available, what it costs, and what actually matters for your home.

First, a quick thing about how gas ducting works

Your gas ducted system blows really hot air — we're talking 60–70°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 40–45°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's not a dealbreaker, but it's something to check 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 things 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 who's 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, hot water, and help you spend your money in the right order.

Your main options

Option 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 means the system can perform as it should.

The upside: Clean slate. Properly designed system that'll actually deliver what it promises.

The catch: More trades, more disruption, and higher cost. If you're doing a renovation anyway and floors or ceilings are already open, this is the time to do it — doing it after is much more expensive.

New ducted RCAC system

Note on keep your existing ducting, and just replacing the unit

If your ducts are in reasonable condition and your home is reasonably well-insulated, you might be able to keep them and just swap out 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.

VEU rebates may be available for a like-for-like replacement — worth checking before you commit.

Old gas ducted system

Option B: Go hydronic — underfloor pipes or radiator panels

This one's 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 air drafts. 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'd still need splits or fan coil units — hydronic doesn't cool the same way. Most people running a hybrid setup keep their existing splits upstairs for bedrooms and use the hydronic system for the main living areas.

This is what Thermal Dawn specialises in.

Hydronic radiator system

Option C: VRF Multi-Head Split System

VRF (Variable Refrigerant Flow) systems sit 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 precisely to match demand across all zones simultaneously. You get individual room control without the running costs of multiple separate compressors. Better for larger homes or multi-storey homes where a single ducted system would struggle to zone properly. Only one outdoor unit to worry about aesthetically.

The catch: Higher upfront cost than individual splits — you're paying for a more sophisticated system. Installation is more involved and requires a specialist. If the outdoor unit fails, all your indoor heads go down at once. Not all installers are experienced with VRF, so getting quality commissioning matters more here than with simpler systems.

Good fit for: Larger homes with four or more rooms to condition, situations where you want individual zone control without visible ductwork, or multi-level homes where a ducted system would need multiple units anyway.

VRF Multi head system

Option D: Forget the ducting entirely, add splits throughout

The most pragmatic option. Rip out the old gas system and put reverse cycle split systems 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 if they're mid-renovation and want a clean finish. Multiple outdoor units can also 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.

Single high wall split system

How to decide

It mostly comes down to three things:

1. 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.

2. Are you renovating? If floors or ceilings are already open, it changes the maths significantly. Hydronic (Option B) becomes much more accessible, and replacing ductwork (Option A) is far less disruptive.

3. How much do aesthetics and zoning matter to you? Individual splits work fine but put a head on every wall. VRF (Option C) gives you the same flexibility with one outdoor unit and potentially better efficiency at scale. Hydronic (Option B) is the most invisible of all — no heads anywhere.

A note on rebates and the cowboys

Victorian Energy Upgrades (VEU) rebates can reduce the cost of electrification meaningfully. But this is also an area where some installers take advantage. A common pattern is recommending an oversized system because rebates often scale with system size — the installer clips a fatter margin and you end up with more than you need.

Get at least one independent quote. Better yet, talk to an energy advisor before you talk to anyone selling equipment. If you want 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 explore Options A, C, and D too, though we're not yet ready to offer rebates on those. We're currently offering pilot pricing for a small number of early customers, and the pricing is genuinely competitive with conventional ducted replacement when you factor in the full picture.

You can read more at thermaldawn.com or register your interest and we'll be in touch.

Thermal Dawn builds hydronic heat pump thermal storage systems for Australian homes. We're based in Sydney and work primarily in Victoria and NSW.