A single-stage furnace means that the valve supplying the burner with gas only has two settings during operation, on full blast and off. They are known as single-speed furnaces because as the name suggests, they work on a single speed. They continuously distribute heated air in the environment at the furnace’s maximum capacity.

Two-stage furnaces utilize a three-position valve that is much more efficient than its single-stage counterpart. The valve settings are on, partially closed, and closed. Therefore, they work at two speeds and operate much more efficiently. The first stage (partially closed state) runs at a 65% capacity and works comfortably in colder climates. And when the temperature drops and stage one heating is not sufficient it switches to stage two heating (on or full blast state) for additional heat. Two-stage furnaces are the most common furnace types used in homes due to their higher energy efficiency model.

Variable speed furnace does not refer to the furnace working at different speeds to achieve desired temperatures, but it rather refers to the blower’s motor/fan speed of the furnace. As the fan is adjustable, it the needed heat to dissipate in the environment by saving your energy costs.

A fully functioning gas furnace works on natural gas. The natural gas is ignited in the furnace providing heat in the environment and this heat can be controlled by an external thermostat. Gas furnaces are the most common heating unit of an HVAC system and are usually paired with a central air conditioner unit installation. They can last between 15 to 20 years.