Replacing ducted gas heating with split systems

Julian, owner of Bright HelpLast checked 17 October 2026

We did it at our house in Torquay in August 2025. The ducted gas heating came out, and a 13 kW multi-head split system went in for our four bedrooms, for $5,400 after rebates. When we decided, I projected it would pay back in about five years.

The house is warmer and drier in winter now, and cooler in summer than a few ceiling fans ever made it.

Why a split system costs less to run

A gas heater burns gas to make heat. A split system is a heat pump: it moves warmth in from the outside air instead of burning anything, which is why it needs about a third of the energy for the same heat.

Ducted heating also loses some of its heat in the ducts, which run through the roof space or between floors, and unless it’s zoned, it heats rooms nobody’s in. A split system puts the heat straight into the room you’re in.

What decides the payback at your house

• How much gas your heating burns. Put a winter gas bill beside a summer one: the difference is mostly heating, since the hot water and the cooktop run all year.
• What you pay for electricity when you heat. With solar, a battery or free midday hours, much of that power costs little or nothing. On a high evening rate, it costs a lot more.
• Whether anything else stays on gas. If the hot water or the cooktop does, so does the gas supply charge. Our hot water still runs on gas, so we still pay a daily supply charge for gas.
• How much gas prices rise over the next few years. Nobody knows, and it moves the payback a lot.

How I got to five years

The five years came from how much gas we were burning each winter, and the price rises forecast at the time, after the invasion of Ukraine and the energy shocks felt around the world. That was the projection when we decided, and how much gas prices rise over the next few years decides how close it comes.

What to ask for in a quote

• Sizing for each room. A head that’s too small for its room runs flat out on cold mornings, and one that’s too big costs more than it needs to.
• Where the outdoor unit goes. It needs air around it and makes some noise, so think about the neighbours’ bedrooms as well as your own. Here on the Surf Coast, salt air is hard on it: ask what protection the unit has against corrosion, and read what its warranty says about living close to the ocean.
• One outdoor unit or several. A multi-head system runs every room from one outdoor unit, which keeps the outside tidy. With separate systems, if one fails, the other rooms keep their heat.
• The rebate. Check the quote for the Victorian Energy Upgrades discount, and whether it’s already taken off the price.
• The old heater. Who takes it out, and who caps the gas to it.
• The paperwork. In Victoria, putting in a split system is electrical work that doesn’t need an independent inspection, so the electrician’s Certificate of Electrical Safety is your record of it. You should get a copy within 30 days.

Draughts and insulation

They change how much heat any system needs, and they matter. I’ll tell you what I notice when I visit, and point you in the right direction if they need work.

When the answer is no

At one house with gas underfloor heating, a heat pump to replace the boiler would have cost $15,000 or more and saved $300 to $600 a year, so more than 25 years to pay back. My advice was to keep the boiler until it’s due, and let a split system they already had do most of the saving.

Where I come in

Before you get quotes, I can work out what your house needs, room by room, and what it should save you. When the quotes come in, I read them. If you’d rather not deal with installers at all, I run the whole job and check it was all done right.