The present invention relates to a thermostat system, to a thermostat unit, as well as to a method for managing power supply in a thermostat unit. A thermostat unit is connected between a power supply and a resistive heating element. Input power is received at the thermostat unit. A temperature difference is calculated between a target temperature and a current temperature. The input power is controlled by operating a power supply module between a heating mode wherein in the input power is channeled to the output port for feeding the resistive heating element based on the temperature difference and a regenerative mode wherein the input power is channeled to an energy storage device for charging said energy storage device in order to supply power therefrom to electronic components of the thermostat unit.