The ideal temperature to run an air conditioner for lower running costs

Start with realistic set points, not fantasy ones

energy.gov.au repeats a consistent message across several household guides: in winter, aim for 18 to 20 degrees, and in summer, aim for 25 to 27 degrees. That guidance exists because every degree pushed beyond a sensible target increases energy use. Once people start treating the controller like an accelerator pedal, they usually create higher bills without getting a better long-term comfort result. [1][2][4]

The mistake many households make is assuming faster comfort comes from a more extreme setting. In practice, the set point tells the system where to stop, not how heroically to perform. Dropping the thermostat dramatically lower in summer or dramatically higher in winter often just extends runtime and encourages uneven temperatures in different parts of the house. [1][3]

That is why the 'ideal' temperature is really the lowest-demand setting that still feels comfortable in the occupied area. For most homes, the answer starts close to the government range and then gets refined by shading, air movement, humidity, clothing, occupancy, and whether the system is conditioning one room or many. A sensible target beats an extreme one almost every time. [1][7][13]

Hyde usually frames this for clients as a control problem rather than a brand problem. If the home feels uncomfortable at a reasonable set point, the first questions should be about sun, leakage, room use, or system fit. Jumping straight to a lower cooling number or a higher heating number often hides the real issue and makes the electricity bill carry the cost of that hidden issue every day. [5][8][14]

Why extreme set points almost always cost more

The official rule of thumb is blunt for a reason: every extra degree of heating or cooling can add materially to energy use. So when a homeowner tries to cool a house to a temperature far below what is reasonable for the weather, or heat it far above what is necessary for comfort, they are asking the system to maintain a bigger gap between inside and outside conditions for longer. [1][2][3]

That cost can be even worse in homes with high heat gain or heat loss. Poor insulation, direct western sun, air leakage, and oversized unshaded glazing all increase the load the system has to manage. Under those conditions, an aggressive set point does not solve the building problem. It simply pushes more conditioned air and more compressor runtime against the same physical weakness. [5][6][7]

Even on well-designed systems, extreme targets can make comfort feel worse. Occupants often end up with one part of the home feeling cold, another still warm, and repeated thermostat changes through the day. The experience feels like the unit is 'working hard' because it is. The more stable and efficient outcome usually comes from a moderate target that the system can maintain steadily. [3][13][14]

This is one reason Hyde spends time on expectation-setting during handover. People do better when they understand that the thermostat is a comfort control, not a sprint command. Once the target is realistic and the home is managed properly, the whole system tends to feel calmer, quieter, and cheaper to run than the stop-start habit of chasing extremes. [1][3]

Comfort is more than the number on the controller

A home that feels good at 25 or 26 degrees in summer is usually doing more than just running refrigeration. YourHome highlights shading, insulation, controlled ventilation, and air movement as major comfort tools, and energy.gov.au points out that fans are cheap to run and improve perceived cooling. That means the most efficient temperature setting is often paired with passive measures, not expected to do all the work alone. [3][7][6]

In practical terms, a ceiling fan or good cross-flow can make a moderate set point feel better than a lower set point in a stuffy room. Likewise, blinds or external shading can reduce how much midday heat the air conditioner must remove in the first place. Lower electricity use usually begins by shrinking the load before the unit even starts. [3][7][5]

The same principle applies in winter. If warm air escapes through gaps, downlights, older doors, or poorly insulated ceilings, the controller setting becomes less relevant because the home cannot hold the result. Sealing and insulation do not just make the house more comfortable. They let reasonable heating settings stay effective for longer, which is where the savings actually appear. [5][6][8]

That is why there is no serious answer to 'What exact temperature saves the most power?' that ignores the house itself. A high-performing home can feel comfortable at a moderate setting because the conditioned air stays where it is useful. A weak building shell forces the HVAC system to chase comfort continuously. The thermostat cannot solve that by itself. [5][7][8]

Use the right setting for the right system

Split systems, multi-splits, and ducted systems can all be used efficiently, but they do not all respond to the same operating habits. Daikin positions split systems as ideal for one room or a defined area, multi-splits as a way to control multiple rooms individually from one outdoor unit, and ducted systems as a discreet whole-home option. The smarter the system layout, the less temptation there is to force the thermostat into doing zoning work it was never meant to do. [10][11][12]

For a single split system in the main living space, the most efficient set point is usually one that keeps that specific zone comfortable without conditioning the rest of the house indirectly through open doors. For multi-splits, the advantage is individual room control, so the lowest-cost setting usually comes from turning on only the heads that are needed. For ducted systems, the value is in zoning discipline rather than letting every outlet run full-time. [11][10][12]

This is also where the Zoned Energy Rating Label matters. The Energy Rating scheme exists because air-conditioner performance varies by climate zone. The label helps buyers compare seasonal efficiency in hot, average, and cold zones, which is especially useful when selecting equipment for a Victorian home where heating performance matters. A better-matched system gives the homeowner more comfort at sensible thermostat settings. [9][14][13]

In other words, the best operating temperature is easier to live with when the unit was selected properly in the first place. Hyde would rather size and zone the system well, then show the client how to use moderate targets confidently, than sell a layout that only feels good when the controller is constantly being pushed to extremes. [9][10][11]

A better Hyde rule for lower running costs

For residential clients, the cleanest rule is usually this: start with the official set-point range, condition only the rooms being used, and lower the building load before lowering the thermostat. That means 18 to 20 degrees for heating, 25 to 27 degrees for cooling, closed doors to unused rooms, sensible shading, and clean filters. It is far less glamorous than a hack, but it is the advice most likely to reduce bills. [1][3][13][14]

If the house still feels wrong at those settings, Hyde would rather investigate why than tell the homeowner to keep nudging the number. Is afternoon sun hitting the wrong glazing? Is the lounge oversized for a small split? Is the return air arrangement poor? Are filters neglected? Is the property losing conditioned air too fast? Those questions usually save more money than another degree ever will. [3][5][7][8]

For Peninsula homes, this matters because building stock is mixed. Some properties are tightly renovated and can hold comfort well. Others are older, lightly insulated, or exposed to coastal conditions and occupancy patterns that make temperature drift more severe. The ideal thermostat setting is not separate from that context. It sits inside it. [6][7][8]

So yes, there is a sensible answer to the question. Start where the official guidance starts, treat the thermostat as a target rather than a weapon, and make the property easier to condition before asking the compressor to do harder work. Lower bills come from discipline, building performance, and the right system choice. The 'ideal temperature' is simply the number that lets those three things work together. [1][2][3]

Choose a system that can hold a moderate target

Moderate thermostat settings only work well when the system is appropriate for the rooms it is serving. A correctly sized split can hold a lounge or main bedroom comfortably without dramatic set points. A multi-split can do the same across several rooms with individual control. A ducted system can deliver a clean whole-home result, but only if the zoning and air-distribution design suit the house. [10][11][12]

This is where climate-aware selection matters. The Zoned Energy Rating Label exists because product performance changes across hot, average, and cold Australian conditions. In Victoria, where heating performance is a real part of the brief, choosing equipment that is better suited to the climate makes it easier to live at realistic settings instead of constantly compensating with the controller. [9][13][14]

Homeowners often think of the thermostat as the main efficiency tool because it is the control they touch every day. In reality, the quieter efficiency win is choosing a system and layout that feel comfortable at moderate targets in the first place. When the hardware and the house are aligned, the ideal temperature stops feeling like a compromise and starts feeling normal. [9][10][12]

What lower-bill operation actually looks like day to day

Lower-bill operation is usually boring in the best possible way. The owner leaves the thermostat in a realistic range, cools or heats the rooms they are actually using, closes off areas that do not need conditioning, and uses curtains, blinds, shading, and fans to reduce the burden on the unit. energy.gov.au and YourHome both keep steering households back to that same disciplined pattern. [1][3][6][7]

It also means keeping the system maintained. energy.gov.au notes that neglected faults and poor maintenance can materially increase energy use, while Sustainability Victoria recommends regular filter cleaning and servicing. A homeowner who wants lower bills but never cleans filters or books service is leaving an easy efficiency gain on the table before the thermostat setting even comes into the conversation. [3][13][14]

If the bills are still high after those basics are in place, the answer is usually investigative rather than behavioural. Look at the building shell, the load on the room, the system selection, and the zoning layout. The right next step is not another degree lower or higher on the controller. It is finding out what is forcing the home to rely on that extra degree in the first place. [5][6][8]

The Hyde takeaway on thermostat settings

The shortest honest answer is that the ideal temperature is the one that lets a well-selected system hold comfort without fighting the building all day. In Australia that almost always starts with the official government guidance range, because those settings are the point where comfort and energy demand are still in a sensible relationship. If a home only feels good when the set point is pushed well beyond that range, the investigation should shift toward the house, the zoning, or the equipment choice instead of pretending the problem is solved by another degree. [1][2][5]

Hyde therefore gets the best outcome by treating the thermostat as the last piece of the chain rather than the first. Start with the building load, the right system class, good room-by-room discipline, and realistic controller expectations. Then the set point becomes easy to live with and the bills become easier to control. Lower electricity use is not created by a secret number. It is created by a house and a system that make a moderate number feel comfortable enough to leave alone. [3][7][10]

That is also why Hyde should be cautious around customers who ask for one perfect temperature as though the question can be answered without context. The more useful service is to explain what is driving discomfort, what range is sensible to aim for, and what changes to the building, the system, or the operating habits will let that range work properly. Once that is understood, the thermostat becomes a stabiliser instead of a daily argument. [1][5][7]