How Do Two Stage Thermostats Work?

By Staff WriterLast Updated Mar 26, 2020 8:47:08 AM ET

Two-stage thermostats run two-stage air-handling systems, which heat and cool in two phases. When the thermostat first turns the unit on, only the first-stage heating or cooling components run unless the second-stage components are needed to maintain a desired temperature.

Two-stage thermostats help with the efficient regulation of two-stage heating and cooling systems, which offer high output for inclement weather and low for more temperate weather. Unlike single-stage systems, which turn on all heating and cooling components at once, two-stage systems turn on only stage one first. If the system can maintain the temperature selected at the thermostat, then only the first stage runs. If the first stage can’t maintain the correct temperature, the thermostat turns on the second stage.

Setting the two-stage thermostat to the low first-stage setting meets regular household needs 80 percent of the time. Although a two-stage system runs for longer periods of time than a one-stage system, it maintains a more consistent temperature by providing more even air distribution. Therefore, two-stage systems are also more energy-efficient because they burn less fuel overall to maintain a desired temperature. Other benefits of the low-stage thermostat setting are that the system runs more quietly and provides better filtration because the whole system doesn’t come on at once.