How to Cut Your Summer Cooling Costs in Melbourne (2026)

The thermostat is free to adjust and it is the single largest lever most households have. Somewhere around 24 to 26 degrees is the sensible summer range for a Melbourne home. Every degree below that adds meaningfully to the running cost, because the system has to work against a larger difference to the outside air and it has to run for longer to hold it.

On a 38 degree day, a house at 24 degrees is fourteen degrees cooler than outside and it will feel genuinely cold when you walk in. Setting 20 does not cool the room any faster, exactly as it does not in winter. The compressor runs at its capacity either way. All the lower setting does is keep it running past the point where everyone was comfortable, then keep it running to hold a temperature nobody needed.

The other habit worth changing is the on and off cycle. An inverter system is most efficient idling at low speed maintaining a temperature, not pulling a hot house back down from 33 degrees twice a day. If the house is occupied through a hot afternoon, holding 25 is generally cheaper and far more comfortable than switching off at lunchtime and blasting at five.

This is the summer counterpart to the same argument we make about heating in our guide to cutting winter heating bills in Melbourne. The physics is the same in both directions.

A reverse cycle split system costs roughly 28 to 36 cents an hour to condition a room. That number holds for cooling as well as heating, because it is the same machine doing the same thing in the opposite direction.

The reason it is that low is that a reverse cycle system does not make cool air, it moves heat out of the room and dumps it outside. For every unit of electricity it consumes it shifts three to four units of heat. Nothing that burns fuel or uses a resistive element comes close to that ratio, which is why the comparison people make between a fan heater and an air conditioner is so misleading.

Put that into a summer. Six hours a day of cooling in a living area at 32 cents an hour is under two dollars a day. Cooling the whole house through a ducted system with every zone open is a different number entirely, which is why the zoning section below matters more than most people expect.

Zoning is the difference between conditioning 40 square metres and conditioning 180. On a hot evening that is most of your bill.

On a ducted system, a zone controller does this properly. Shut the bedrooms during the day, shut the living areas at night, and the system moves the same air into a smaller space, which means it reaches temperature sooner and holds it with less run time. If your ducted cooling has zones that have never been set up correctly, that is a cheap fix with a real return.

On split systems, zoning is free. Close the doors. A single head in the living room cooling the living room is efficient. The same head trying to cool the living room, the hallway, three bedrooms and a stairwell through open doors is a system that will be blamed for being undersized when it is actually being asked to do a different job.

The other useful habit is sequencing. Cool the bedrooms for half an hour before bed rather than running them all evening, and use ceiling fans in occupied rooms to raise the temperature you find comfortable. A ceiling fan does not cool air, it moves it across skin, but it reliably makes 26 degrees feel like 24 for a fraction of the energy.

This is the trick that changes the economics for any household with rooftop solar, and almost nobody uses it.

Melbourne hot days follow a pattern. Generation peaks in the middle of the day. The house heats up through the afternoon. The occupants get home around five or six and turn the air conditioning on hard, precisely when the sun is dropping, the grid is at its peak and the tariff is at its worst.

Pre-cooling inverts that. Run the system from around eleven in the morning to three in the afternoon on solar generation you would otherwise export for a few cents, and pull the house down to 23 or 24 degrees while the power is effectively free. The building fabric holds that. When everyone gets home the system has far less work to do, and what it does have to do starts from a much better position.

This works best on a home with reasonable insulation, because a leaky uninsulated house loses the pre-cooling within an hour. It works even better with a home battery, which lets the evening run on stored generation instead of peak grid power. Our guide on whether a home battery is worth it in Melbourne west works through those numbers. With feed-in tariffs where they now sit, self consuming generation is worth considerably more than exporting it.

Cooling a house that is absorbing heat all day is a losing position. In Melbourne the dominant summer heat gain is direct sun through glass, particularly west facing glass in the late afternoon, and heat soaking through an uninsulated ceiling.

External shading beats internal shading by a wide margin. Once the sun has come through the glass the heat is inside, and a blind can only re-radiate some of it back out. An awning, an external blind, eaves or a well placed deciduous tree stops the heat before it enters. If you only do one thing to a west facing living room window, do it outside.

Ceiling insulation is the other one, and it is the same fix that saves you in winter, which is why it is such a good investment. A roof space in Melbourne on a 38 degree day can sit well above 50 degrees. Batts that are missing, compressed, or have been shoved aside by tradespeople over the years let that radiate straight into the rooms below all afternoon and well into the evening.

Draught sealing matters less in summer than winter but it still counts, particularly on hot windy days from the north when hot outside air is being pushed into the house through every gap. The same door seals and exhaust fan dampers that keep heat in during July keep it out in February.

This is the most neglected item on any maintenance list and the one with the highest return for the time it takes. A blocked filter on a split system or a ducted unit makes the fan work harder to move less air. The room takes longer to reach temperature, the compressor runs longer, and the whole system underperforms in a way people consistently mistake for the unit being too small or being on the way out.

Split system filters lift out of the indoor head and rinse under a tap. Do it at the start of the season and again halfway through if the house is dusty, has pets, or backs onto a main road. Let them dry properly before they go back in.

Beyond the filters, an outdoor unit needs clear airflow. Something that has been fine for five years stops being fine when a hedge grows across it or someone stacks boxes against it in a side passage. The condenser has to reject heat into the outside air, and it cannot do that in a dead pocket of air behind a fence.

For ducted systems, filter replacement and a proper service before summer catches the things you cannot see, including refrigerant charge, which is a licensed job. A system low on refrigerant still runs, still blows air, and quietly costs you a great deal more per hour than it should.

Melbourne is genuinely a reasonable climate for evaporative cooling, which is not true everywhere in Australia. Our hot days are usually dry, with the humid weather arriving mostly with the change rather than ahead of it.

Evaporative cooling pulls outside air through wet pads and blows it through the house, with windows or doors open to let it out again. It uses very little electricity because it is a fan and a pump rather than a compressor, and it delivers a large volume of fresh air. It works well on a dry 35 degree day and it is cheap to run.

Where it struggles is on the muggy days, because it works by evaporating water into the air, and air that is already carrying moisture will not take much more. On those days an evaporative system moves a lot of warm damp air through the house and people describe the result as sticky rather than cool. It also uses water, needs the house open, and cannot be zoned in any meaningful way.

Refrigerated cooling, which is what a split system or refrigerated ducted system delivers, works regardless of humidity, dehumidifies as it runs, can be zoned, and is the same equipment that heats the house in winter. It costs more to run per hour than evaporative but it does more, and the reverse cycle heating side is a large part of the value. Our comparison of evaporative versus refrigerated cooling in Melbourne works through the trade offs properly, and if you already have an evaporative system it is worth servicing before you replace it.

If you are working through this across a couple of seasons rather than all at once, the order is much the same as it is for heating.

Change the setpoint and the zoning habits first, because they cost nothing and take effect the same afternoon. Clean the filters second. Shade the west facing glass third, because it is cheap relative to its effect. Fix the ceiling insulation fourth, and note that it pays back twice a year rather than once.

Replace the equipment last, once the building is behaving, so the new system is sized for a house that holds temperature rather than one that leaks it. A split system installed runs $2,500 to $7,500 depending on capacity and how many indoor heads are involved, and our split system installation cost guide covers where in that range a job lands. Victorian Energy Upgrades discounts come off the invoice directly with no income test, provided the property is at least two years old, and the program changed on 30 September 2026, so we confirm the current figure in writing at quote.

Refrigerant work requires an ARC licence and the electrical connection requires a licensed electrician issuing a Certificate of Electrical Safety. We do both in house. To get a fixed price on a system or a pre-summer service, contact us or call 0401 500 446.