Honeywell's two-stage thermostats are designed to work with heating systems that offer two different heating profiles. Two-stage technology is available for both the programmable and non-programmable thermostats.
Traditionally, heating systems could only be turned on or off. As a result, systems would run for long periods of time when it was cold outdoors and in short bursts on milder days. Since systems operate most efficiently when run cycles are longer, two-stage heating systems have been developed. During cold periods, systems operate at full power, keeping the home warm; during milder days, they produce less heat for longer periods of time, leading to better efficiency. Two-stage systems allow users to choose which heating profile to use, which leads to lower heating bills.