What Does the "Two Stage" Feature of a Gas Furnace Mean?

How a Two-Stage Gas Valve Works

A two-stage gas furnace has a gas valve that operates at two output levels instead of one. On a mild day, the furnace fires on the lower stage, which uses less fuel and produces a gentler, longer heating cycle. When the thermostat calls for more heat on a colder day, the valve automatically opens to the higher stage and the furnace delivers its full capacity. This lets one furnace match a wide range of conditions instead of running flat out every time it turns on.

Lower Fuel Use and More Even Heat

Because the furnace spends much of the heating season on its lower stage, it can reduce your fuel bill by about 20 percent compared with always running at full output. The longer, lower-stage cycles also heat your home more evenly. Instead of frequent blasts of full-capacity heat followed by long off periods, the furnace provides steady warmth that holds temperatures closer to your setting. That means fewer hot and cold swings between rooms and a quieter system, since the blower and burners run at reduced output much of the time.

Single-Stage vs Two-Stage at a Glance

Is a Two-Stage Furnace Right for You?

Two-stage furnaces tend to make the most sense in climates with a real heating season and in homes where even comfort and quieter operation matter. If your winters are short and mild, a single-stage unit may be all you need. AC Direct sells gas furnaces in single-stage, two-stage, and modulating designs so you can match the furnace to your climate and budget, backed by the AC Direct Price Promise and free technical support.