Understanding Furnace Stages

The various furnace stages refer to how hard the blower needs to work to provide hot air for your home. In a single stage furnace, the furnace is always running at 100 percent capacity, even if your home doesn’t need very much heat. Multi-stage furnaces were developed as a way to save energy by running the furnace’s blower at a lower capacity when 100 percent heating capacity isn’t necessary.

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Multi-Speed Furnaces are More Efficient

Multi-speed furnaces, also known as multi-stage or variable-speed furnaces, run at several energy levels. Multi-stage furnaces can cut the blower capacity down to as low as 40 percent, so you can have the right level of heat you need and save money and energy. Multi-stage furnaces are more costly, but they can have annual fuel utilization efficiency above 94 percent. The most advanced multi-stage furnaces also are able to recycle exhaust heat.

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Two-Stage, Three-Stage, and Multi-Stage

A two-stage furnace is also sometimes called a multi-stage furnace. However multi-stage furnaces can have more than just two stages. Two-stage furnaces have low and high options, while three-stage furnaces have low, medium, and high settings. If you want a true multi-stage furnace, you will enjoy more than just two or three efficiency levels. Some furnaces can be used with a smart thermostat to get the desired level of efficiency for even more energy savings.