Ideal Air Conditioner Temperature | Save Power & Sleep

The efficiency of your unit depends on a range of factors—where you live, the type and size of your system, how you use it, and more. And with so many variables, how do you determine the ideal air conditioner temperature for your unit?

In this article, we’ll explain how.

The ideal AC temperature changes between regions

Quite simply, yes. The most efficient air conditioning temperature can be influenced by the climate and the seasons of where you live. These factors affect how hard your unit needs to work to keep your home warm or cool. 

But climate is more than just temperature—it is a combination of environmental factors including rainfall, humidity, wind and daylight hours. For example, if you’re in a rainy or high-humidity environment, your air conditioner will have to work harder to regulate the temperature. Other factors like wind can increase the atmospheric dust conditions which can clog filters.

Because air conditioners have to work harder to offset extreme temperatures, people living in warmer climates should set their cooling temperature a little lower. Conversely, those living in cooler climates should set their heating temperature a little warmer. However, it’s important to remember that while efficiency is important, so is comfort. And although air conditioners can be expensive to run, the optimal temperature is one that strikes a balance between comfort and how much you’re willing to pay for electricity.

Optimum temperatures for air conditioning

To ensure a unit’s maximum efficiency, a standard air conditioner’s temperature in a moderate climate should be set to 25 to 27°C for cooling in summer. In terms of what temperature to set an air conditioner in winter, 18 to 20°C is ideal for heating. However, as well all know, in Australia we experience a range of climates and weather conditions. Here is a general guide to heating and cooling settings, based on your location.

Why is adjusting the temperature for sleep important?

Sleep and our body’s temperature are deeply interconnected. In fact, biologically, our ability to enter a natural wake-sleep cycle is governed by it. Scientists believe our body temperature impacts the quality and amount of sleep we receive each night. But how does our core body temperature work in tandem with our sleep cycle?

During the day time, our core body temperature fluctuates constantly, and our brain does this naturally without us noticing. At night, when our bodies wind down, our core body temperature starts to decrease to a lower, healthy temperature to usher us into the sleep cycle. 

But why do hot and cold temperatures at night wake us up? The answer is scientific. During rapid eye movement sleep (REM) — which is the most important sleep for memory consolidation and body repair — our brain’s temperature regulating system switches off. Therefore, the room’s temperature becomes the main way our body regulates its own temperature. With the wrong room temperature, we risk creating poor sleep patterns, including irregular, uncomfortable hours of disrupted sleep.

The best air conditioner temperature for sleeping varies from person to person, depending on our comfort levels. However, experts believe that cooler temperatures work better than warmer temperatures because they assist our body’s core temperature to drop, and the recommended sleeping temperature is around 18°C.

Sleep mode function

The “sleep mode” function on an air conditioner is the ideal way to regulate the temperature of the room where you sleep. It works in harmony with your body’s body’s natural sleep cycle to help you sleep more soundly. Some more info on how it works:

• Once your unit is turned on, the inverter will work hard to achieve your selected temperature.
• Once the preferred temperature is achieved, the inverter will decrease power to consume less energy, while still preserving the ideal temperature.
• The unit will then increase the temperature by half a degree for four hours, allowing you to wake up at the ideal temperature.

If you air conditioner also has an intelligent movement sensor: 

• Your unit will gradually go up half a degree per hour to slowly warm the room.
• If it detects movement in the room, such as the tossing and turning that often indicates a disturbed sleep, it will bring the temperature of the room back to its starting temperature to help ease you back into sleep.
• When it senses you have returned to a comfortable sleep, it will slowly raise the temperature before shutting off. 

How does the set temperature affect power bills?

The harder your air conditioner has to work, the more electricity it will consume. So essentially, the higher you set your unit’s temperature when heating and the lower you set it when cooling, the more you are adding to your power bill. It is difficult to exactly determine how much your unit’s temperature is contributing to your electricity usage costs, but it’s been estimated that every degree cooler in summer adds around 10% to the amount of electricity your unit is using. 

Below is the hourly cost of air conditioning cooling temperature settings, based on a 28.479 c/kW electricity usage rate. Although the running costs across various temperatures look relatively minor, they can certainly add up!

Source: Canstar Blue

To explain the effects in a practical example, say you use a 6kW cooling capacity split system air conditioner every evening for five hours throughout summer, at a unit temperature that’s always set to 21°C. As per the above table, the usage will cost you 50 cents an hour or nearly $2.50 per day. However, if the unit is running like this for a period of ninety days during summer, air conditioning will cost you $225 on your quarterly electricity bill. However, if you set your unit to 24°C, it will cost thirteen cents less per hour, and cost around $166 for the same period—a saving of over $58!

What’s the right-sized air conditioner for my home?

It’s always a good idea to consult an air conditioning specialist if you’re trying to determine your air conditioner size, as there are many factors involved. But here’s a rough guide.

To cool or heat efficiently, an air conditioner should generally have at least 80 watts of output per square metre of room. If a room is larger than your unit is designed to cater for, it will be less effective at controlling the temperature. So for example, the settings may say that it is set to cool at 24°, however the room temperature may actually be 28°. Conversely, if a room is too small for a unit, it will over-shoot the temperature you intended to set it to. Below is an approximate guide to the ideal air conditioning capacities according to room size.

How can I maximise my air conditioner’s efficiency? 

Setting your unit to the recommended temperature for your location is one strategy we’ve covered, but here are other factors to consider:

Choose an energy-efficient model

The best long-term strategy to maximise your unit’s efficiency is to avoid putting excess strain on it. Essentially, the harder your air conditioner has to work to heat or cool a room, the more electricity it will consume and the higher your power bills will be. If your unit is too small, it will have to work harder to warm up the room it’s situated in. If it’s too big, it will have a shorter cooling cycle. Both will use up more energy and add to your electricity bills.

You can check how much energy your unit uses by comparing the cooling and heating input and output of different models, and energy rating labels are a great way of doing this (but unfortunately, aren’t available for ducted systems). These labels are based on a star rating (from one to six), which measure both cooling and heating efficiency. Red star ratings demonstrate its heating efficiency, blue stars rate their efficiency when cooling. The more stars a unit has, the more energy efficient it will be and the cheaper it will be to run. Super-efficient models will have a rating of between seven and ten stars.

Use the right settings

The settings on many modern air conditioners can also help with efficiency, including their thermostats. The role of a thermostat is to regulate your air conditioner to stay at the temperature you’ve set. However, all units take time to remove moisture and humidity from the air. The difference between the set and ambient temperature will also affect how long the room will take to heat or cool. The smaller the difference between the inside and outside temperatures the lower your electricity usage will be.  

When cooling, it’s worth remembering that setting the thermostat to the coolest temperature will not cool your home any quicker. For example, if you want your home to be at a comfortable 22 degrees, setting the temperature at 18 degrees will not regulate the temperature any faster. As we’ve mentioned previously, every degree colder you set the unit can cost up to ten per cent more on your power bills. 

In terms of heating, many reverse cycle air conditioners are equipped with an automatic “defrost” mode — when your system is heating inside, it is also cooling outside. In below-zero temperatures where frost and ice build-up is common, your unit will actively monitor the outdoor coil temperature as well as the indoor ambient temperature. Once the coil temperature becomes too cool, the unit will initiate the defrost cycle.

 Some air conditioners also come with an “economy” mode that can help maintain a moderate temperature, and some with human sensor features that automatically switch the system to an energy saving mode when no movement is detected in the room.

Use your system’s timer

Most air conditioning systems include programmable, timed thermostats, so you’re not only setting the temperature, but setting the hours of operation for minimal energy output. This can reduce the number of hours your unit is actually running, and maximise its efficiency.

For example, timers can be used to start cooling a bedroom on a warm night before you plan to go to bed. They can also switch on your unit before the temperature outside gets too hot. This is because at the beginning of the day, the air outside and inside your home is generally cooler, which means the air conditioning system uses less energy to reach the set temperature you need throughout the day. Switching the air conditioner on during the hottest part of the day puts an excessive amount of pressure on a system, makes it work much harder, and it will take longer to cool down your home.

It’s also worth noting that it is more expensive in the long run to leave your unit running when you’re not home as opposed to switching it on or off, or using a timing to set it to when you need it or return home. This is because even if the temperature is set to the existing ambient temperature, the compressor is still running, and that’s the part of the unit that uses the most energy! 

Focus on ventilation and insulation

To improve air conditioner efficiency, the most obvious strategy is to only warm or cool the rooms you need. However, you can also focus your heating or cooling on the most commonly used rooms, and seal off others by closing doors which will contain the warm or cool air. Drafts should also be minimised by repairing door seals or using door snakes or weather strips to block any gaps.

Ventilation can be maximised by opening windows to let the cool air in and removing plants, furniture or curtains that are obstructing indoor components. Cleaning up any foliage or dust on an outdoor unit and covering it with a shade cloth or awning can also stop it from overheating. The heat load can also be reduced by turning off internal heat sources like printers, computers and lights.

If you are undertaking renovations or building a new home, there are a number of structural ways you can increase your home’s energy efficiency. Insulation can be installed in walls, pipes, ceilings and roof spaces to reduce heat loss in winter and heat gain in summer. Skylights can help natural light enter your home during winter, double glazed windows can trap cool or warm air, and exterior shadings like awnings, shutters, drapes, blinds and tinting allow sunlight in during the day in winter and reduce the amount of sun entering rooms in summer.

Service your air conditioner

Air conditioning units essentially help to filter bacteria and dirt from the air, but it also means they consume a lot of debris. And although this consists of small airborne particles, it leads to dirty filters and clogged ducts that can make a unit work much harder, which means more electricity is being used.

Filters should be cleaned and vents and exterior components dusted regularly (you can do this yourself), but you should also schedule in a regular service with a professional (twice a year is recommended). They will typically flush the drains, measure the airflow, clean the ductwork, replace any filters if necessary, top-up the refrigerant and check the motor’s efficiency. 

Old units are also often overworked and components can result in further strain on your unit (ie. lower efficiency), so if you have an older model, it may be time for a replacement. Newer models have a range of energy-efficient features and must adhere to the government’s Minimum Energy Performance Standards (MEPS).

Consider ducted air conditioning

Ducted air conditioning can be an energy efficient option to consider if you have a larger home. It gives you the freedom to heat or cool your whole house at the touch of a button and works by pumping air throughout a system of vents. Temperature “zoning” also segments the areas of your property and allows you to concentrate your heating and cooling efforts where they are needed most.

For example, you can cool or heat living areas during the day and bedrooms at night and not waste energy on targeting empty or unoccupied rooms. And although it can be more expensive than other systems to install, you only have to pay for one system, including ongoing servicing and maintenance costs.

Most ducted systems also offer timer settings that allow you to pre-program your air conditioner to come on at predetermined times, and Wi-Fi connectivity, so you can fully automate your system and operate it remotely from your device or smartphone.

Installing ducted air conditioning also makes good financial sense if you are planning to eventually sell your home. This is because ducted air conditioning is regarded by many as a luxury or high-end property feature and can increase your property’s value.

Understand the market

To increase your home’s energy efficiency, including saving on your electricity bills, it’s worth shopping around for a retailer that suits your power usage and your individual needs. Many offer discounts if you pay on time and/or via Direct Debit. Others will offer you benefits if you switch to a fixed plan or contract for a nominated period.

The continually increasing competition in the market also means many providers are now focused on providing even more opportunities for customers to save on their power usage. So keep a close eye on your electricity bill, keep up to date with changes in the industry, and switch providers if you don’t think you’re getting the best deal possible.

References

• 2019, What is your air con temperature setting costing you? Canstar Blue
• 2021, Energy-efficient air conditioning incentive, Energex
• Dr.Heather Wright, 2020, The Best Temperature For Sleep: Advice & Tips, Sleep Foundation