Air‑conditioning technicians agree: As a general rule, you should never force your AC unit to go below 75°F

It’s a familiar summer routine. After a long day at work, you walk into a hot, stuffy house, grab the air conditioner remote, and immediately set the temperature to 66°F, or even 61°F, thinking it will cool the house faster. In reality, that’s a common mistake, and here’s why.

How an air conditioner works

An air conditioner doesn’t work like a car’s accelerator. Lowering the thermostat doesn’t make the system blow colder air or increase the airflow. It simply tells the unit what indoor temperature to reach.

According to Spanish energy company Endesa’s blog, “Setting the thermostat to 66°F in an attempt to cool the room faster only makes the system work harder and increases energy consumption without speeding up the cooling process. Keeping the temperature within the recommended range is both more efficient and healthier."

When you set the thermostat unnecessarily low, you force the compressor to run continuously. On especially hot days, the system may never be able to reach a setting as low as 66°F. As a result, it operates at full capacity for extended periods, increasing wear on critical components and raising the likelihood of costly breakdowns during the peak cooling season.

The Recommended Temperature

Many HVAC professionals recommend maintaining a consistent indoor temperature between 75°F and 79°F for the best balance of comfort, efficiency, and energy savings.

Experts also advise keeping the difference between the outdoor and indoor temperatures to no more than about 22°F. Larger temperature gaps increase the workload on the air conditioner, reduce efficiency, and may make the transition between indoor and outdoor environments less comfortable.

Don’t overlook maintenance

Endesa also emphasizes that regular maintenance is essential for keeping an air conditioner operating efficiently and extending its lifespan. Routine maintenance includes cleaning or replacing the air filters, inspecting the condensate drain and cooling system, checking refrigerant levels, and cleaning the outdoor unit to ensure proper airflow and performance.

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