Reverse Cycle Ducted Heating for Melbourne Homes

A ducted reverse cycle system has four parts that matter to you. There is an outdoor unit that sits on a slab or brackets somewhere along the side of the house, an indoor fan coil in the roof space or under the floor, the duct network and outlets, and a controller that talks to zone motors. Everything else is detail.

The indoor unit is where the old gas furnace used to live in a lot of changeovers, which keeps the job tidy. The outdoor unit is new territory for gas customers, and its position needs thought because it runs for long stretches in winter and sits close to bedroom windows on narrow blocks.

Sometimes, and we will tell you honestly on site. Gas ducted air leaves the furnace at roughly 55 to 60 degrees, while reverse cycle supply air is closer to 35 to 45 degrees. To deliver the same warmth at a lower temperature, the system has to move considerably more air. Ducts that were fine behind a furnace can become a bottleneck behind a heat pump.

The checks are practical. We look at duct diameter against the required airflow, the condition and R value of the insulation, whether runs have been crushed by storage or foot traffic, and how big the return air grille is. On a lot of 1990s and 2000s homes in Hoppers Crossing and Werribee we keep most of the branch runs, upsize the return air, and replace a handful of outlets. On older or badly sagged systems, new duct is the cheaper answer once you count the callbacks.

Capacity is quoted in kilowatts, and the right number comes from room volume, insulation, glazing, orientation and how open the plan is. Floor area on its own is a guess. A 20 square metre lounge with a raked ceiling and a west facing sliding door needs materially more capacity than a 20 square metre bedroom with a single window and batts overhead.

Oversizing is the more common mistake. A unit with too much capacity reaches setpoint fast, shuts down, then restarts, which wastes energy, leaves warm and cold patches and shortens compressor life. Undersizing shows up on the three or four genuinely cold mornings a year when the system runs flat out and never quite gets there. We measure, we ask what the house does through the day, and we size to the middle of the sensible range.

Zoning is where most of the real saving lives. Motorised dampers open and close groups of outlets so the system heats a day zone in the evening and a night zone overnight. Three zones covers the majority of houses we do, typically living, bedrooms and a third for a study, rumpus or the far end of a long floor plan.

One honest limitation. Zoning does not create extra capacity, it redirects it. Every ducted system needs a minimum airflow to run safely, so you cannot run a single small bedroom zone on a large unit without a bypass or a variable speed indoor fan. We design the zone groups so the smallest combination you would realistically use still keeps the unit inside its operating range.

On the numbers we see, a reverse cycle system heats a room for roughly 28 to 36 cents an hour compared with 50 to 72 cents an hour for ducted gas, which lands between $200 and $450 a year for a typical household once you account for the gas supply charge you may also be able to drop.

Victorian Energy Upgrades discounts come off the installation invoice directly, so there is no rebate to claim afterwards and no income test. The property must be at least two years old and the scheme carries a minimum customer contribution of $200 including GST. The program changed on 30 September 2026, so we confirm the current amount in writing at quote time rather than quoting a number that may have moved.