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Three Stages

Although there is never a good time to replace your ailing furnace, fall is a popular time for this service. Should yours need replacement, you might consider three of the following furnace models.

  1. Single-Stage Furnace

The single-stage furnace, also called a one-stage furnace, operates with only two settings: “on” or “off.” When it is on, it is at the maximum level of heat output, with no adjustment for how warm or cold it is outside or within different areas of your home. Because this type of furnace is always on “high,” it lags in energy efficiency behind the other options.

  1. Two-Stage Furnace

The two-stage furnace is a step up in efficiency from the single-stage furnace, with two stages that allow for some adjustment for changes in outdoor temperature. Most (about 75%) of the time, this type of furnace operates in the first or low stage which is approximately 65-75% of the furnace’s capacity, saving on energy. When the outdoor temperature drops and more heat is needed, the second or high stage engages to meet the current heating requirements for as long as necessary. Once the outdoor temperature warms up again, operation returns to normal, so you are only paying for the additional energy when you need it. Because of the lower output most of the time, the furnace does run longer, but this also allows for more even heat distribution. Two-stage furnaces have quieter operation, are more efficient and are better for the environment.

  1. Variable Speed Furnace

The variable speed furnace offers the most flexibility in terms of operation and energy use. Instead of stages, this furnace relies on a fan motor and gas valve that operates at different varying speeds to adjust the amount of heat output produced. Variable airflow results in greater comfort, because temperature is more consistent throughout the home and better air quality because air goes through the filter more often. Even when the furnace is not heating, air can continue to circulate, which actually reduces the need for it to turn on as often. This results in energy savings and lower utility bills. An added bonus: the variable speed furnace is quieter than the single-stage or two-stage furnaces. Not only will this furnace save gas but it will also save a considerable amount of electricity over standard models.