For use with central gas, oil, heat pumps with auxiliary heat, electric furnaces and air conditioning. Works with millivolt systems. Does not work with electric baseboard heat or multi-stage heating/cooling systems. Up to 4 periods per dayprogramming. Digital 2Heat/1Cool. Easy to read green backlit display. Precise temperature control of +/- 1 F (degree fahrenheit). Early start function adjusts the pre-heating/cooling. Basic operation keeps programming simple, and installation requires 15 minutes or less. Includes mounting hardware.