Thermostat Voltage is an electrical voltage that is used to remotely control the temperature settings of a given device. It is typically employed in temperature-controlled ducting systems and HVAC systems, and can be used to notify a remote power source when a predetermined temperature setting has been reached. It is important to ensure that the correct voltage level is used in order to successfully regulate the device, as using too high or too low a voltage can lead to errors or malfunction of the appliance.