Most Melbourne homes heat at least one room with gas: a wall furnace in the lounge, a space heater, or a ducted system that runs from May to September. If you’re wondering whether a reverse-cycle split system really is cheaper to run, the maths is simpler than most sales pitches make it look.
Compare the cost of a unit of heat
The fair way to compare is to work out what each system charges you for the same amount of heat delivered into the room. Using round numbers that are typical for Victoria in late 2026:
- Gas heater: gas at about 4.2 cents per megajoule, and a heater that turns about 75% of that gas into useful heat once flue losses and cycling are counted. One kilowatt-hour of heat (3.6 MJ) costs roughly 20 cents.
- Reverse-cycle split: electricity at about 30 cents per kWh, and a modern inverter split delivering around 3.5 to 4 units of heat for each unit of electricity across a winter. One kilowatt-hour of heat costs roughly 8 to 9 cents.
So the split system delivers the same warmth for well under half the running cost, before you count solar. Your own prices will differ, but it takes a very cheap gas tariff or very expensive electricity to close that gap. You can put your own figures into our gas vs electric running cost calculator.
Where the comparison gets messier
- Cold mornings. A heat pump’s efficiency drops as the outside temperature falls, and it pauses briefly to defrost the outdoor coil on frosty mornings. In Melbourne this rarely matters much, but in colder spots it narrows the gap a little.
- Old or oversized units. A 15-year-old split, or one that’s far too big for the room, won’t hit the efficiency figures above. Neither will one running flat out all day in a draughty room.
- Whole-house gas ducted. Ducted gas often has extra losses through ducts in the roof space. That usually makes the reverse-cycle comparison even better, but replacing a whole ducted system is a bigger job than adding one split.
Sizing a split for a living area
For heating, a split is usually sized by the room’s heat loss rather than floor area alone. As a very rough guide for a reasonably insulated Melbourne living room with a 2.4 m ceiling:
- up to about 25 m²: 2.5 to 3.5 kW
- 25 to 40 m²: 5 to 6 kW
- 40 to 60 m² open plan: 7 to 8 kW
Big windows, high ceilings, poor insulation or an open stairwell push those numbers up. A good installer should work it out room by room and quote the heating capacity, not just the cooling capacity printed on the box.
Check the label
Air conditioners sold in Australia carry the Zoned Energy Rating Label, which shows separate heating and cooling star ratings for hot, average and cold climate zones. Melbourne falls in the cold zone, so look at the heating stars for that zone. Brands publish these figures on their range pages; Daikin’s split system range is one example of where to find them.
Running both while you transition
You don’t have to rip out gas heating to start saving. Many households put a split in the main living area, use it for most of the heating, and leave the gas system for the coldest weeks or the rest of the house. When the gas unit eventually needs replacing, you already know how well reverse-cycle suits your home. Our all-electric upgrade order shows where heating fits in the bigger plan.
Figures and rules in this guide were checked in November 2026. Rebates change often, so confirm current amounts on the official sites linked above.