When and What Setting is an Air Conditioner Most Efficient?


I was finding ways to improve the efficiency of my air conditioner and I wonder when is an air conditioner most efficient. Thus, I did some research.

An air conditioner is more efficient at night because the outside air temperature is colder. The air conditioner uses outside air to reject heat. Colder air rejects more heat and increases the cooling capacity of the air conditioner while maintaining its power consumption.

Most people get it that cold air brings away more heat and so, the air conditioner is running more efficiently. But, why colder air can boost the efficiency of an air conditioner?

Why is an Air Conditioner Most Efficient with Colder Air?

The efficiency of an air conditioner is measured in terms of its coefficient of performance (COP). The higher the COP, the lesser the power consumption and thus, we say that the air conditioner is more efficient.

At night, the ambient air temperature is lower. The colder air absorbs more heat during the condensation process which happens at the outdoor unit of an air conditioner. Consequently, the cooling capacity of the air conditioner increased.

Based on the COP formula, the increases in cooling capacity will result in a higher COP for the air conditioner. Therefore, the air conditioner is more efficient.

Is it Cheaper to Run AC All Day or Just at Night?

As a general rule, it is cheaper to run the air conditioner just at night rather than all day. An air conditioner is most efficient at night due to the colder outside air temperature. In addition, the air conditioner requires less work at night because the room temperature is lower.

Some people think that if they turn on their air conditioners at night, their rooms are warmer, the air conditioner spikes in power usage and consume more electricity. Therefore, they are wondering if they should run their air conditioner during the day to bring down the room temperature first.

In fact, they shouldn't because it doesn't save you any money to run your air conditioner all day to try to flatten the energy spike. Conversely, it only makes you pay more for the electricity bill.

Tips to Use Your Air Conditioner Efficiently

Other than letting the outside temperature control the efficiency of your air conditioner, you can apply the tips below for your air conditioner to run efficiently:

  • Avoid overcooling: set your indoor temperature between 26°C and 28°C.
  • Put a curtain to your windows to reduce external heat gain.
  • Regularly clean your air conditioner filter and coil as necessary.
  • Turn off the switch or breaker when not using your air conditioner for a long period of time.
  • Ensure all windows and doors are closed when using the air conditioner.

Condenser Pre-cooling Mist System

Many companies offer condenser misting systems in an effort to help their customers to reduce air conditioner power consumption.

Best ac in USA | The Best Air Condi...
Best ac in USA | The Best Air Conditioner In USA: Complete Guide - See before Purchase

A condenser misting system is a supporting accessory which sprays fine mist (water) around the condensing unit to reduce its surrounding temperature and increase the efficiency of the air conditioner.

Unfortunately, this system comes with downsides such as insignificant saving, long ROI and risk of coil damage.


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Yu Chang Zhen

I enjoy working on air conditioners and ventilation fans because Malaysia is a very hot country.

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