Replacing ducted gas heating with reverse-cycle: the honest cost-benefit
Across south-east Melbourne, gas heating is on the way out. New gas connections are banned in new builds. Existing units are pushing 15–25 years old. And reverse-cycle is now cheaper per kWh of heat delivered — even before the VEU rebate.
But the answer to "should I rip out the gas heater?" isn't always yes. Here's the honest version.
Where reverse-cycle wins
- Older gas unit (10+ years) with 60–70% efficiency
- Insulated home with R3+ ceiling and reasonable double-glazing
- Open-plan living that doesn't need every zone heated equally
- You also want cooling — one system, both seasons
- You have or will get solar — daytime heating becomes near-free
- VEU rebate applies — up to $5,000 off the install
Where ducted gas still makes sense
- Very large home (300m²+) with high ceilings — gas heats fast cheaply on cold snaps
- No roof space for the outdoor condenser
- Recently replaced gas unit (under 5 years old, 90%+ efficiency) — payback period is too long
- Holiday house with low use — fixed costs swing in favour of gas
The numbers for a typical Pakenham home
A 4-bedroom Pakenham home (180m² living), single storey, R3 ceiling:
| Annual heating cost | |
|---|---|
| Old ducted gas (75% efficiency) | ~$2,100 |
| Modern ducted reverse-cycle (COP 4.0) | ~$680 |
| Modern reverse-cycle on daytime solar | ~$220 |
| Annual saving vs old gas | $1,420–$1,880 |
Install cost: typically $10,500–$14,000 for a 12–16 kW ducted system installed, before rebate. After up to $5,000 VEU, you're looking at $5,500–$9,000 net. Payback: 4–6 years, depending on solar.
Things people forget to ask
Can I keep the existing ductwork?
Usually yes — most existing ducts are oversized for gas and work fine with reverse-cycle. We test airflow during the survey. If ducts are damaged or undersized, you'll get the rough cost up front.
Do I need to zone it?
Zoning (3–8 zones) gives you up to 30% additional efficiency and avoids heating empty bedrooms. Reverse-cycle benefits from zoning more than gas because the unit modulates capacity. Worth it on any system 14 kW or larger.
What about cold snaps below 0°C?
Modern inverter reverse-cycle units run efficiently down to -10°C. In Pakenham's coldest mornings (-2 to +2°C) you might see capacity drop 15% — still adequate for a properly sized system. Coastal Mornington Peninsula and Brighton: no issue at all.
Our recommendation
If your gas heater is 12+ years old and you're considering its replacement: upgrade to reverse-cycle now. The maths is decisive after rebate, you remove a CO risk, you gain cooling, and you future-proof against gas disconnection.
If your gas is under 8 years old and working well, ride it out 3–5 more years. The rebate's likely to still be there, and electricity prices are stable enough that the maths only improves.
FAQ
Will my house feel different to heat?
Reverse-cycle heats slower than gas — about 20 minutes to reach setpoint instead of 5. But the air feels gentler (less drying), and once at temperature, modulation keeps it more consistent.
Can I keep gas for cooktop only?
Yes. Many of our customers retain gas for cooktop while removing the heater. Reduces but doesn't eliminate the gas supply charge.
How long does a ducted retrofit take?
2–3 days on site for a single-storey. Day 1: old unit out, condenser placement, duct survey. Day 2: indoor unit, controller, electrical. Day 3: commissioning, balancing, customer walkthrough.