Why Does The Air Conditioner Consume More Electricity When It Cools to A Lower And Lower Temperature?

In summer, people always say to not turn on the air conditioner at too low a temperature or it will consume more power. Why is this sentence true? Psychological advice or a real physical reason?

I. The lower temperature setting, the larger temperature difference, the higher power consumption

The core task of the air conditioner is to "transfer heat"—transfer the heat from interior to exterior.

Setting a cooling temperature at 18℃ means the air conditioner needs to transfer more heat from a hotter environment to the outside.

It relates to a concept here: the higher the temperature difference (ΔT), the more heat needed to be transferred, and the requested power in each cooling unit will increase.

· Set at 26℃ with a small ΔT, the air conditioner operates at ease.

· Set at 18℃ with a large ΔT, the air conditioner needs a higher compression ratio to keep the cooling effect.

The higher the temperature difference, the more the air conditioner operates at a high burden all the time, and then the energy consumption rises sharply.

II. The higher compression ratio, the lower energy efficiency

The energy consumption of the compressor is related to the compression ratio.

When the setting temperature decreases:

· The evaporating temperature decreases; the compressor needs to compress the low-pressure refrigerant into high-pressure. Then the compression work per unit mass of refrigerant has significantly increased.

· Particularly when the setting temperature is 18°C, while the compressor is operating at full speed or high frequency, resulting in a decreased efficiency and increased power consumption.

III. Longer operation period to reach the setting temperature and higher electricity consumption

The room temperature does not change to 18℃ immediately when we click the button; instead, it must decrease from the common temperature steadily.

And it will take longer to reach the designated temperature if the room has poor insulation, a large size, and a high heat burden.

During the process, the compressor will operate for a long time under high burden, the indoor airflow will keep at a high level, and the whole system will hardly move to the "low frequency level." As a result, the energy consumption increases.

IV. The lower temperature, the higher dehumidification burden

The cooling process is accompanied by dehumidification normally. The lower the temperature, the lower the evaporation-surface temperature decreases, the stronger the condensation effect, and the more potential heat the refrigerant needs to take away because the moisture evaporation requires energy. It means an additional heat burden and an extra energy consumption.

V. Actual experience: 26℃ is more energy-saving and more comfortable

The coolness comes from not only the room temperature but also the wind speed, humidity, airflow direction, and body heat transfer. Too low a temperature may not be more comfortable; instead, it will lead to the following problems:

· high temperature difference → getting cold easily;

· over-dry temperature → uncomfortable skin;

· direct cold airblow → headache and shoulder/neck tension.

The most suitable temperature setting is 26℃ with medium wind speed and slight humidification, which is energy-saving and comfortable.

VI. How to keep the same temperature with less electricity?

1. Don't set the temperature at the lowest level at the beginning.

Set it to 26℃ first, cool the room first, and then adjust the temperature according to our feelings.

2. Work with fans, accelerate the circulation

Through which the air conditioner can reduce its cooling level and save more electricity.

3. Avoid frequent start-ups

Particularly for the non-inverter air conditioners, restarting the air conditioner would consume more electricity.

4. Keep the filter clean

Blocks on the filter may lead to higher system pressure and higher energy consumption.

5. Close the curtain and avoid the heat

It reduces the sunlight coming in and reduces heat burden; as a result, it saves energy.