Is your AC usage driving up power consumption?
How can you maximize cost savings on your electricity bill when using an air conditioner? To answer this question, we spoke with Chikashi Shigemasa, an “Air Evangelist” at Daikin Industries, who shared his insights on several common misconceptions regarding energy savings when operating air conditioning systems.
We often hear advice on how to operate air conditioners efficiently: “Set the airflow to the lowest setting,” “Cover the entire outdoor unit to prevent direct sunlight exposure,” “Turn off the AC regularly when not in use, even for short periods,” or “Point the airflow downward to focus cooling on the floor-level area where people are active.” Interestingly, all four methods may actually be counterproductive. You could even call them “wrong techniques for saving energy.”
“It is crucial for us to understand how an AC cools a room, which components consume electricity, and their respective energy consumption levels. This understanding provides a clear picture of which steps are truly effective for saving energy, while also building confidence in making future AC usage decisions,” says Shigemasa.
A serious concern arises when people avoid using air conditioners to save energy, only to negatively impact their health. As a manufacturer specializing in air conditioning systems, we recognize our growing responsibility to provide accurate education on effective AC usage. With the right knowledge, users can enjoy indoor comfort while still achieving optimal energy savings.
Key AC Components Account for Up to 80% of Electricity Consumption
“The compressor, often referred to as the “heart” of the AC, accounts for approximately 80% of the total electricity consumption during operation,” explains Shigemasa.
Simply put, an AC cools a room by drawing indoor air into the Indoor Unit to absorb heat, then returning the air in a cooler state after the heat has been removed. The heat absorbed from the indoor air is then transferred to the Outdoor Unit via a gaseous substance called refrigerant, which flows through the connecting pipes between the two units.
Next, the Outdoor Unit releases this heat into the outside air. Throughout this entire process, the compressor plays a vital role by compressing the refrigerant and circulating it through the piping system. This process enables efficient heat absorption and rejection, allowing the room to be cooled optimally.
When aiming to save energy, reducing airflow volume or fan speed is actually not recommended. Lowering the airflow causes the AC to take longer to absorb heat from the room, thereby increasing the workload on the compressor. While higher airflow may make the Indoor Unit sound louder and initially appear to draw more power, in reality, the fan motor consumes significantly less electricity than the compressor motor.
Therefore, setting the airflow to “auto” mode is considered far more effective. During the initial stage, the AC increases airflow to accelerate heat absorption. Once the room temperature begins to stabilize, the system automatically switches to a more steady operation. This operational pattern helps reduce compressor load while maintaining comfortable room temperatures with better energy efficiency.
Additionally, the compressor experiences high workload when the AC is first turned on. This is why the advice to “frequently turn the AC on and off” can actually increase electricity consumption, depending on usage duration and frequency. An experiment conducted by Daikin showed that leaving the AC running for about 30 minutes during the afternoon actually yields better energy savings compared to repeatedly turning it on and off.
Poor Airflow Increases Compressor Workload
“Given how an AC absorbs heat from indoors and releases it outdoors, one key to energy savings is ensuring that airflow pathways remain clean and unobstructed,” says Shigemasa.
To ensure smooth airflow, it is important to clean the Indoor Unit filter and keep the area around the Outdoor Unit tidy. If dust accumulates on the filter, the volume of incoming air decreases, reducing the AC’s cooling capacity. Consequently, the unit must work harder for longer periods to cool the room, ultimately increasing electricity bills.
Furthermore, if the filter is not cleaned for a year, unnecessary electricity consumption is estimated to reach approximately 25%.※1 Similarly, when the Indoor Unit filter has accumulated dust for about three years and objects around the Outdoor Unit hinder air circulation, electricity consumption can more than double. Therefore, I recommend cleaning the filter once every two weeks to keep the AC operating efficiently and saving energy.
As mentioned earlier regarding some ineffective energy-saving tips, some people cover the Outdoor Unit to protect it from direct sunlight. However, when obstructions block the air intake or exhaust, heat cannot be dissipated efficiently. Keeping the area around the Outdoor Unit clear and free of objects that obstruct airflow will help prevent unnecessary electricity consumption.
※1 Annual electricity cost ratio is calculated based on operational conditions per JRA4046-2004 with and without filter cleaning (1145 kWh), as well as 1432 kWh based on a 2-gram dust volume accumulation after one year (Source: Daikin Industries).
More Even Room Temperature Allows the Compressor to Operate More Efficiently
Shigemasa highlights that to reduce the load on the compressor, it is equally important to minimize “temperature stratification” within the room.
“The air conditioner detects room temperature based on the air drawn into the Indoor Unit from the room. In rooms with uneven temperatures, air near the ceiling tends to be warmer. When the AC draws this air, it determines that ‘the room temperature has not yet reached the set point.’ Even though the floor-level area where people are active is already sufficiently cool, the AC will continue to run longer than necessary, leading to increased power consumption. Therefore, we must ensure that the airflow from the AC during cooling is directed horizontally, not downward. Cold air is denser and tends to settle near the floor. By directing cold air horizontally along the ceiling, it will naturally descend to the floor from above, making it easier to eliminate temperature stratification.”
Directing airflow horizontally also helps prevent discomfort caused by the AC blowing air directly onto occupants. To minimize temperature differences, air purifiers, fans, and air circulation controllers can be used to mix the air. The motors driving these devices consume very little power compared to the AC compressor. When temperature differences are minimized, the compressor load can be reduced, leading to lower power consumption and energy savings while maintaining a comfortable and cool environment.
