Ducted or a split in every room: what each costs to run

The yearly bill with every room on

If you are choosing between ducted air conditioning and a split system in each room, the running cost is the part you keep paying every year. So we priced both for the same house, from the official energy figures.

Five splits for a four bedroom house cost $1,039 to $1,397 a year to run. One ducted system of about the same size costs $1,143 to $1,936. Where you land in each range depends on the models you pick.

At the efficient end, the splits come out $104 a year ahead. But those totals assume every room runs for the same number of hours. Your house may not work that way, and that is where the two options really split apart.

Our example house, room by room

Here is the house we priced: an open plan living and kitchen area of 50 m², a main bedroom of 20 m² and three bedrooms of 15 m² each. That is 115 m² of rooms to cool and heat.

We sized each split with Mitsubishi Heavy Industries' sizing chart, the one we use across this site. For each room we took the smallest size the chart allows for a brick or brick veneer room with an insulated roof, facing east.

That gives a 7.1 kW split for the living area, 3.5 kW for the main bedroom and 2.5 kW for each of the other bedrooms. Each size is a group, as on our size pages, so the 3.5 kW group includes 3.3 kW models.

Here is the lowest and the highest yearly cost among the models we install in each size, cooling and heating together:

The lowest figures come from the Daikin Alira X 7.1 kW, the Daikin Alira X 3.5 kW and the ActronAir Serene 2.6 kW, which sits in our 2.5 kW group. The highest come from the Daikin Skywall 7.1 kW and the Mitsubishi Electric MSZ-EF at 3.5 and 2.5 kW.

The totals are worked out before rounding, so the rows can add up a dollar out. You can see every model in each size, cheapest to run first, on the 7 kW, 3.5 kW and 2.5 kW pages.

One ducted system of about the same size

The five splits add up to 18.1 kW. We install six ducted systems at 17 and 18 kW that carry official figures. We hold no figures for two more at 18 kW, the Daikin Slimline and the LG, so they are left out.

With every room on, the cheapest set of splits beats the cheapest ducted system by $104 a year. Even the dearest set of splits, at $1,397, comes in under three of the six ducted systems.

Three of the six also need three phase power. If your switchboard is single phase, that narrows the choice, and the single or three phase guide shows how to check.

We compared like with like here, the same total size. How big a ducted system your house actually needs is a separate question, and the ducted cost guide explains what sets it.

What the official figures assume

Every figure here comes from the government's GEMS energy register, for Sydney's climate zone. We priced them at 31.79 cents a kWh, the median usage rate across 170 Ausgrid plans in September 2026, including GST.

The register gives each unit a yearly energy figure from a standard test. We checked what that figure assumes, using the register's own numbers. For almost every registered unit, small or large, it comes to the same thing: running at full capacity for about 400 hours of cooling and 550 hours of heating a year.

That makes the figures a fair way to compare one unit with another. It also means our example runs each bedroom split as hard as the living room one, for the same hours.

In a real house the bedrooms might run at night and the living area during the day. Your bill follows how you use the house, not the test.

Where splits pull ahead, and where ducted does

With splits, a room you are not using costs nothing to cool, because its unit is off. If you only ever ran the living room split, the official figures put it at $464 to $594 a year.

A ducted system can shut off rooms too, with zones. But there is no official figure for a ducted system running with some zones closed, so we won't put a number on it. The ducted cost guide linked above explains how zones work and what they add to the install.

Ducted has its own strengths. There is one indoor unit in the roof and one outdoor unit outside, and each room gets a ceiling grille instead of a unit on the wall. Five splits means five indoor units on your walls and five outdoor units outside.

There is a middle option too: a multi-split runs several wall units from one outdoor unit.

These are running costs only. We don't publish installed prices, and the installation cost guide explains why. The totals include a winter of heating. The heating guide breaks that part down, ducted included.

Working it out for your house

Your rooms won't match our example. The calculator gives you a size for a room from five quick questions, and the compare page lines up the running costs of any models side by side.

Or send us a few photos of the rooms, the roof space and the switchboard with a quote request. We'll recommend what fits your house, ducted or splits, with a fixed price in writing before any work starts.

Sources

• GEMS registered air conditioners dataset (E3 program), data.gov.au, CC BY 3.0: the yearly cooling and heating energy for Sydney's climate zone, the power supply of every model named here, synced 1 September 2026. The 400 and 550 hours are our own arithmetic from the dataset's yearly energy, seasonal efficiency and rated capacity columns (download of 22 September 2026): 98 in every 100 units fall between 378 and 421 hours of cooling and between 544 and 586 hours of heating.
• Energy Made Easy, the AER's plan data: the median usage rate across 170 Ausgrid plans, September 2026, with GST added: 31.79 cents a kWh.
• Mitsubishi Heavy Industries split systems brochure, page 4: the sizing chart, the largest room each size suits by room type.