Use this Honeywell digital thermostat with low volt heating and cooling systems. You can use it with several types of low volt systems such as millivolt and single-stage heat pumps. Auxiliary heat isn't required. The temperature control of +/-0.5 °C is accurate. The thermostat has a large backlit display. It's easy to toggle between Celsius and Fahrenheit. Custom features include four programmable periods per day, plus weekday/weekend programming. When used as directed, this thermostat can save you up to 33% on energy costs.