The thermostat for an air conditioning unit is a device used to regulate the temperature inside of a building or residence. It functions as a regulator, allowing users to set a desired temperature and maintaining it within an acceptable range. The thermostat can interact with other components in the system, such as the fan and compressor, to maximize efficiency and reduce energy consumption. It is important that the thermostat is correctly calibrated and monitored regularly, since any degradation in performance may result in higher running costs.