–How to Control the AC Temperature at Home

According to the US Department of Energy, as a general rule, you should be setting your air conditioner at 25ºC (or 78ºF). In some countries, policies are being passed to set an established temperature by default on new air conditioning units, as an effort to prevent energy waste and to direct consumers to what is considered an acceptable temperature.

The reality is that the actual ideal home temperature can change from household to household because there are many factors that play a role in your home’s comfort. Humidity, season, ventilation… These elements can alter thermal sensation and understanding them can give you a better idea of what is the best temperature for your home.

Thermal sensation and thermal comfort

Your air conditioning’s temperature setting may be different to what the real thermal sensation is. Thermal sensation refers to our perception of the temperature, and it can be a couple of degrees above or below the actual air temperature. Meanwhile, there is the concept of thermal comfort, which refers to the temperature being just right, not too warm nor too cold. The difficulty with thermal comfort is that it varies from person to person, and factors such as our clothing can also influence it.

Factors that affect your home’s ideal AC temperature

There are some factors that alter the way we perceive temperature and our thermal comfort. Which are these factors and how do they affect our home’s temperature?

• Humidity. Have you experienced humid hot weather? What about dry cold seasons? The sticky and stuffy feeling from high humidity makes a hot summer day even more suffocating. Just as dry weather makes winter days more uncomfortable and harsh. Humidity is measured as a percentage, related to the total amount of water the air can hold at a certain temperature. When relative humidity (RH) is high (over 80% RH), sweat cannot evaporate; and when it is low (below 20% RH), our respiratory system suffers and our noses and throats tend to dry, causing irritation and higher risk of infection. According to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) keeping RH between 30% and 60% is recommended, as in this range there is little to no impact on thermal comfort. Air conditioners help in removing excess moisture from the room, if you are dealing with high RH, run the AC in dry mode. And if low humidity is your concern, using a humidifier can do the trick.

• Season. Those of you that live in countries with defined seasons will know that the ideal AC temperature range is different in summer and winter. This is because weather factors drastically change temperature, both outdoors and indoors. During summer, there are more sunny days, and there is more sunlight throughout the day, contributing to the heat. Some regions also experience higher humidity levels during summer, which makes hot days feel even hotter. During winter, we typically get less sunlight, with shorter days. In some regions freezing temperatures are common, undergoing frost and snow. Despite modern houses’ better insulation, we are not immune to the effects of seasonal changes indoors.

• Ventilation. Airflow moves air around, increasing the sense of cooling without lowering the room’s temperature. You may have experienced this when increasing the fan speed while running the AC. In the same way, cool drafts during winter can make you want to heat up the space. Taking advantage of natural ventilation or fans during the warm season can help lower energy consumption. Meanwhile, preventing cool air from filtering in through window and door gaps during colder months will help maintain a warm temperature indoors. Another way ventilation helps amplify comfort is by drawing moisture out, which is key in certain areas, such as the kitchen and the bathroom. Here, exhaust fans to expel steam will keep excess moisture away and reduce the likelihood of mould, mildew or other bacteria from proliferating.

• Room occupancy. We naturally expel heat and moisture by breathing, moving and sweating. So the more people occupying a space, the more heat will add up. If you live alone and you have guests over, your air conditioner may have to work slightly longer than usual to cool off or warm up the room. But instead of lowering the temperature, you can use the powerful mode on your AC, which will function at maximum power for a few minutes to quickly cool or heat the room and reach the desired temperature in less time.

• Type of activity. When doing more physical tasks, such as exercising or cleaning, we expel more heat than while doing sedentary activities. However, the amount of heat we produce depends on many other factors, such as height, weight or fitness level. For this reason, certain temperature settings may be right for some, while too warm or too cold for others. So, if thermal comfort is the goal, the best temperature for your home may not be the same as that for another person.

How does an air conditioner’s temperature work?

To understand how your air conditioner achieves the temperature you set, we need to cover first how it operates. The way your split or multi-split air conditioner works is by pulling the room’s air inside the indoor unit and blowing it around the evaporator coil, through which the refrigerant flows, the heat is extracted from the air, and is then dispersed through the outdoor unit; finally, the conditioned air is blown back into the room. Learn how air conditioning works, here. 

Normally, air conditioners rely on sensors equipped inside the indoor unit that measures the temperature of the air that is being drawn in. This is referred to as the “return air” when the sensor detects that the return air matches the temperature setting, the AC stops. Inverter models keep running at lower power to save energy while maintaining the desired temperature.

Ideal temperature at home

What temperature should you set your home air conditioner on? As mentioned at the beginning of the article, the US Department of Energy gives the general recommendation of 25ºC (or 78ºF). However, the actual answer depends on when you are using your AC. Let’s see some of the most common situations:

• Temperature and comfort. If thermal comfort is your goal, ASHRAE recommends setting your AC to a temperature somewhere between 20ºC to 23ºC (68ºF-74ºF) during winter, while during summer it is recommended a range of 22ºC to 27ºC (72ºF-80ºF), with an RH range of 30% to 60%.
  
  
• The ideal temperature for sleeping. When going to sleep, our bodies slightly drop their temperature. It is our bodies’ way to signal the brain into sleeping. This is why it is more difficult to sleep in a warm room. Sleep experts say that to encourage sleep, the room should be at a temperature of around 18ºC (65ºF). However, as personal preferences differ, the range can be anywhere between 16ºC to 19ºC (60ºF-67ºF). A way to help you sleep better while saving energy is to program the AC to achieve this temperature at bedtime and then power it off, so you aren’t awakened by excess cold. Some ACs also have a Sleep Mode, as found on Hitachi Residential AC, that gently increases the temperature by 1ºC every hour. Learn more about temperature and ambience tips in our article about improving your sleep quality.
  
  
• Temperature for exercising. As we have mentioned previously, more intense physical activities make us expel more heat and sweat, which can reduce thermal comfort. If you do at-home workouts, fitness experts recommend setting your AC between the range of 20ºC to 22ºC (68–72ºF) to exercise in comfort and to prevent overheating.

How do I control the temperature of my air conditioner?

Now that you have an understanding of the ideal temperature to set on your air conditioner, let’s take a look at how you can control it and make the most out of your air-con.

• Remote controls. Remote controls are a convenient and easy way to access your AC’s settings and modes with the touch of a button. Some common modes are eco mode, powerful mode, sleep mode and timer. Remote controls usually have a display screen where you can see the temperature and mode settings. Adjust the temperature using the up and down buttons.
  
  
• Thermostats. Thermostats differ from controllers, as they are installed on a wall inside the room, where it provides readings for the temperature in that spot. The location of the thermostat is key for accurate temperature readings, which is why it shouldn’t be installed in hot or cold spots. Thermostats allow basic controls for setting the temperature and turning the appliance on and off.

• Smart controls. Modern ACs include some smart features that can enhance your comfort while saving on energy. These features can automatically adjust the AC’s power. For example, activity sensors that detect human presence to power on or power off, or adapt the settings to provide better comfort. Some smart ACs also detect when the user has gone to sleep, to adjust the temperature for better sleep.

• Apps. Smart air conditioners are recommended to use with their dedicated smartphone apps. These allow you to use your smartphone as an AC controller, control your AC remotely, monitor your AC use and energy consumption, and activate geofencing. Using an app unlocks many features to fully enhance your AC experience. For example, Hitachi’s P-Series smart wall mount opens up all these possibilities, and when paired with the airCloud Go app, it takes care of your comfort for you, letting you forget about the AC.

Balancing comfort and energy consumption

It is possible to use an air conditioner without compromising on efficiency. There are many ways you can save on your electric bills, even while using your AC for the ideal comfort. Here are some tips:

• The best temperature for energy saving in comfort is 25ºC (78ºF) during summer and 20ºC (68ºF) during winter, according to the US Energy Department. As a general rule, the less difference there is between your AC temperature in comparison to the outdoor temperature, the less power it will consume.
  
  
• Use fans to enhance your AC’s cooling ability without lowering the temperature. Make your AC work smarter and not harder by increasing the fan speed or by complementing your AC with a conventional fan.
  
  
• Install curtains or shades to reduce heat impact from sunlight during summer. Sunlight can add a few degrees to your home’s temperature, which may not be ideal during summer, but is perfect to reduce heating consumption during winter. Open your window’s curtains to let your home soak in the sunlight during the day to enjoy a cozier evening.
  
  
• Choose the right size air conditioner for your home. The ideal air conditioner for your home depends on its size. Larger homes or rooms need larger capacity ACs. Choosing the wrong size of AC can unnecessarily increase energy consumption or put too much stress on the appliance.
  
  
• Use smart features to automatically set the temperature for different times of the day. On hot days, you may need a cooler temperature around midday or noon. Schedule your preferred settings in advance, so that the AC cools exactly when you need it the most.

Hitachi Residential Air Conditioners for the Ideal Comfort All Year Round

Creating a comfortable and efficient home environment in all climates is simpler with Hitachi Residential air conditioning. In this article we touched upon various features and functions that the Hitachi Residential air conditioner range offers for cooling and heating needs to help you maintain the perfect temperature in your home, no matter the weather outside. Learn more about our ranges and all their benefits here.