Why does my laptop fan turn on?

Answer: Laptops are designed to be compact. Their sleek design makes them easily portable but also creates challenges when managing heat. Because the components inside a laptop are tightly packed together, they can heat up easily. Airflow inside the laptop is essential to keep the components from overheating.

Most laptops include one or more small fans that keep air flowing inside the computer. Typically, the fans are quiet and unnoticeable. However, when CPU usage nears 100%, or the battery is charging, it creates extra heat. When the internal temperature sensors hit a certain threshold, the fans speed up to cool the laptop. A high speeds, fan noise is often audible.

▶ Fans are more likely to run at or near full speed when a laptop is plugged in. Laptops may employ energy-saving strategies when running on battery power to extend the length of the battery. Examples include limiting CPU usage and dimming the display. When you plug in your laptop, these throttling measures are removed, and your computer may run hotter.

If your computer's fans are consistently loud, you can look for processes that are using a significant percentage of the processing power. Active processes are listed in the Task Manager (Windows) or Activity Monitor (Mac).

If no processes are using near 100% CPU, your laptop may have insufficient airflow. You can use compressed air to clean out dust or have your computer cleaned by a hardware technician.

Published: February 11, 2021 — by Per Christensson