Always closing the door tightly when turning on the air conditioner

Recently, social media has been flooded with tips on how to save electricity when using air conditioners. Some people suggest that you must keep the door completely closed while using the AC so that the cold air doesn't escape, the room cools faster, and the unit isn't overworked.

After reading this information, Ms. Nguyễn Thị Hảo (32 years old, from Nam Định) agreed, sharing that her house has three bedrooms. In each room, she installed a 9000 BTU air conditioner. Whenever the unit is running, she always reminds her family members to close the doors tightly.

"I believe that if the door is left ajar or people keep going in and out, the cold air will escape, making the unit work harder and consume more electricity. So usually by 9 PM, everyone heads to their rooms, closes the doors, and rarely goes out," Ms. Hảo shared.

Although he values energy saving, Mr. Nguyễn Thanh Tùng (from Hoàng Mai, Hanoi) believes that sometimes, a room needs to “breathe,” and people also need fresh air circulation.

According to Mr. Tùng, if a room with an air conditioner is sealed for hours, it becomes stuffy. Users may feel stifled, heavy, and lack oxygen to breathe. While keeping the door shut may save electricity, it’s not good for your health.

Addressing these concerns, Professor Dr. Nguyễn Đức Lợi from the Vietnam Association of Refrigeration and Air Conditioning Engineers said that closing the door while the AC is on can help save power. However, the room should not remain completely sealed for extended periods.

“During air conditioner use, fresh air intake is necessary—about 20 cubic meters per hour per person. This fresh air is hot and comes from outside, so the AC must use energy to cool it. If a room has a fresh air supply system (such as in office buildings, malls, hospitals), then it’s appropriate to keep all doors closed to save energy.

But in residential homes without such systems, owners should allow air in by leaving a window or door slightly open. Families can also install a wall fan with proper airflow to support ventilation.

It’s best to run the air conditioner for about 3–4 hours, then turn it off to ventilate the room, and then run it again,” Professor Lợi advised.

Sealing the room tightly with AC on isn't always good—experts share the proper approach
Avoid keeping rooms sealed too long—every 3–4 hours, allow for ventilation. (Photo: Hồng Anh)

💡 Tips to Keep Your AC Room Cool and Efficient

According to Professor Nguyễn Đức Lợi, for an air conditioner to work efficiently and save power, homeowners should note the following:

• Proper design calculations: Ensure correct cooling capacity.

• Choose the right unit: Buy from reputable brands with clear origins, and opt for inverter models.

• Proper installation: Use genuine materials, proper specifications, and ensure work is done by skilled, ethical technicians. Use the shortest gas pipes possible with minimal elevation differences.

During installation, technicians must vacuum the system, add oil and gas correctly, remove air pockets, choose optimal installation spots, and provide sunshades for outdoor units and windows.

Windows should have indoor sun-blocking curtains and, if possible, external curtains—especially for east- or west-facing windows.

• Correct placement of the outdoor unit: It should be installed in a well-ventilated area, free from swirling wind, exposed to outdoor air for proper condenser cooling, and away from extreme heat or dust. The outdoor unit must be on a solid base, close to the indoor unit, and easy to maintain.

• Correct placement of the indoor unit: Install it where the cool air can spread evenly, without obstructions, and close to the outdoor unit. Gas pipe length should be between 3–5 meters, and condensate drainage should be easy.

• Maintenance and repairs: Dirty or dusty units severely impact performance. Therefore, regular cleaning and timely repair are essential.

The expert added that in summer, air conditioners often run continuously. During extremely hot periods, non-inverter models may overload and shut down to protect themselves.

Inverter ACs may continue to operate, but the compressor slows down, reducing cooling capacity and possibly not reaching the desired indoor temperature. This is due to the unit’s self-protection mechanism.

All air conditioners have a maximum outdoor temperature limit—typically from 38°C to 53°C. When buying a unit, families should select one rated for the local climate.