A humidistat is a built-in sensor that measures the relative humidity (RH) of the air and controls the dehumidifier’s operation. It ensures that the dehumidifier turns on and off automatically to maintain a set RH level, usually between 30-50%. This prevents over-dehumidification, which can lead to dry air and discomfort. By regulating the RH level, the humidistat helps to optimize the dehumidifier’s performance, reduce energy consumption, and provide a comfortable indoor environment.