A programmable thermostat senses the room temperature and controls the HVAC system according to a schedule established by the homeowner. This type of thermostat allows different temperature settings to automatically regulate the HVAC system at different preset times.
A thermostat is usually the least costly component of a HVAC system. It can play a major role in the energy efficiency of the HVAC system. The goal of a setback thermostat is to regulate the HVAC system to maintain a desired comfort level when the home is occupied and then enter an economizing mode when the house is unoccupied. A double adjustment, during work hours and sleep hours, will result in the greatest energy savings in the summer and winter. A single adjustment to an economizing mode each day also contributes significant savings.
Other conserving thermostats include electromechanical thermostats with setbacks and occupancy thermostats. The electromechanical types are lower cost and use bimetallic strips associated with a vial of mercury to make or break an electric current to operate the HVAC equipment. An occupancy thermostat maintains an energy conserving temperature until someone enters a room and presses a button to increase the temperature for a short period of time.
Programmable thermostats can require some effort to learn and master them. Several programmable units can accommodate different settings for every day of the week.