Here is a scene we run into every summer. It is a 34-degree afternoon in Gosford, the house is still warm, so someone sets the air conditioner to 18 and waits for the room to feel like a fridge. An hour later it is comfortable, but the unit has not switched off once and the power bill is quietly climbing. The best temperature for an air conditioner is almost never the coldest number on the remote, and setting it that low rarely cools the room any faster.
After more than 15 years servicing homes across the Central Coast, we get asked the same thing when the heat arrives: what number should I actually set it to? Here is the honest answer, with the reasons behind it, for both the hot months and the cold snaps.
The number that suits most homes in summer
For cooling, aim for somewhere between 24 and 27 degrees. Australia’s energy guidance (energy.gov.au) recommends setting your air conditioner between 25 and 27 degrees in summer, and notes that every degree higher can save roughly 5 to 10 per cent on the running cost. That is a real difference over a long, humid Central Coast summer.
Most people find 25 or 26 degrees perfectly comfortable once the room settles, especially with a fan moving the air around. If you like it cooler, 24 is a sensible floor. Dropping below that is where the bills start to bite for very little extra comfort.
Why setting it to 18 does not cool the room faster
This one surprises people. Your air conditioner cools at a steady rate no matter what you set the thermostat to. Setting it to 18 instead of 25 does not make cold air come out any harder or sooner. All it does is tell the unit to keep running long past the point the room was already comfortable, so it works harder, longer, and often overshoots into that clammy, over-cooled feeling.
Think of the thermostat as a destination, not an accelerator. The number you choose decides when the unit stops, not how quickly it gets there. If you want the full picture on where your dollars actually go, we broke it down in our guide to what it costs to run your air conditioner through a coastal summer.
What to set it to when you are heating in winter
Plenty of Central Coast homes run a reverse cycle system, which heats as well as cools. Winter mornings in places like Wyong and the valleys behind the coast get cold enough that people reach for the heat, and the same logic applies in reverse. For heating, 18 to 20 degrees is the comfortable, efficient range for most households.
Cranking it to 25 in winter has the same effect as setting it to 18 in summer. The wider the gap between the outside temperature and your setting, the harder the system works and the more it costs. A jumper and 19 degrees will almost always beat a t-shirt and 24.
The setting that helps most while you sleep
Overnight, bodies cool down naturally, so you can usually nudge the temperature up a degree or two from your daytime setting without noticing. Many units have a sleep or timer mode that gently raises the set temperature through the night and switches off before morning. It is one of the easiest ways to stay comfortable and still wake up to a smaller bill.
Coastal humidity changes how the number feels
Here on the coast it is often the humidity, not the raw heat, that makes a room feel sticky. When the air is damp, 25 degrees can feel warmer than the same 25 on a dry day. If your system has a dry or dehumidify mode, running it on a muggy afternoon pulls moisture out of the air and can leave the room feeling cooler at a higher, cheaper setting. Homes near the water in Terrigal, The Entrance and Woy Woy tend to notice the difference most.
When the room never reaches the number you set
Sometimes the setting is right and the room still will not get there. That is usually the unit telling you something. Clogged filters, dirty coils, low refrigerant or an undersized system all stop an air conditioner from holding the temperature you have asked for, so it runs flat out and never quite catches up. In our coastal climate, salt and dust build up on the coils faster than most people expect.
If your system is running constantly and still not hitting the mark, a professional air conditioner service will usually sort it out and often pays for itself in lower running costs. For the settings and habits side of things, we also put together some simple ways to cut your cooling costs that work alongside choosing the right temperature.
Straight answers about air conditioner temperatures
Is 22 degrees cold for aircon?
Twenty-two is on the cooler side for a Central Coast home and most people will feel it. It is comfortable, but you will use noticeably more power than at 25 or 26. If you like it a little brisk, 22 is fine on the hottest days, just expect a higher bill if you leave it there all summer.
Is 24 degrees hot for AC?
Not at all. Twenty-four degrees is a comfortable, efficient cooling setting for most homes and sits right at the sensible lower end of the range. With a fan running, plenty of households find 24 to 26 is all they need on a warm day.
Is 25 degrees too hot for a room?
For a cooled room in summer, 25 degrees is close to ideal. It feels comfortable once the space settles, keeps humidity in check and is one of the most energy-friendly settings you can choose. If it still feels warm, a ceiling or pedestal fan usually makes 25 feel more like 23.
Is 18 degrees cold for aircon?
Yes, 18 is very cold and it is the setting we see cost people the most. It does not cool a room any faster than 25, it just keeps the unit running far longer. Unless you genuinely want a fridge-like room, there is little reason to set it that low.
What temperature should I set my air conditioner at night?
A degree or two above your daytime setting works well, so around 25 to 26 in summer. Your body cools while you sleep, so you rarely need it as cool as during the day. A sleep timer that eases the temperature up and shuts off before morning is ideal.
What is the best temperature for reverse cycle heating in winter?
Aim for 18 to 20 degrees when heating. That range keeps most Central Coast homes comfortable without making the system work overtime. Every degree higher adds to the cost, so it pays to start at 19 and only nudge up if you need to.
Getting the temperature right is the cheapest upgrade you can make to your comfort, but a system has to be in good shape to hold it. If yours is struggling to reach the number on the remote or running non-stop through the day, get in touch with our team and we will book you in for a service across the Central Coast, from Gosford and Erina through to Toukley and Umina Beach.
