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An Overview Of The Three Major Types Of Gas Furnaces

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According to the U.S. Energy Information Administration, at least 47% of American households used natural gas (2015 data) as their main source of heating. However, many people don't know that gas furnaces come in various forms. Below are the three main types of gas furnaces to explore when shopping for a gas furnace. 

Single-Stage Furnace

A single-stage gas furnace is the simplest form of gas furnaces. The furnace has only two settings for its control: on and off. That means the furnace is either running or not. You turn the furnace on when you need heating — it doesn't matter whether you need a little or a lot of heating output. You turn the furnace off if you don't need any heating.

Here are some of the advantages of single-stage furnaces:

  • They are relatively inexpensive.
  • They are less likely to malfunction than other furnaces.
  • They have low repair costs.

On the other hand, single-stage furnaces also have disadvantages, for example:

  • They are energy inefficient.
  • They are prone to uneven heating (when areas around the thermostat heat faster or more than other areas).
  • They are noisy since they always run at full blast.

Keep these pros and cons in mind if you have been considering a single-stage furnace.

Two-Stage Furnace

A two-stage furnace represents the next stage (after single-stage furnaces) in the evolution of furnaces. A two-stage furnace has three basic settings: off, on-low, and on-high. The low setting produces less heating than the high setting. Thus, you can set the furnace to either low or high, depending on how cold your house is.

Here are some of the advantages of two-stage furnaces:

  • They are energy efficient since you don't have to run them at full blast all the time.
  • They provide even heating.
  • They are not as noisy as single-stage furnaces.

Unfortunately, you still have to worry about these disadvantages of two-stage furnaces:

  • They cost more to purchase and compared to single-stage furnaces.
  • They are more likely to break than single-stage furnaces.

Modulating Furnace

Modulating furnaces represent the crème de la crème of the gas furnace evolution. Modulating furnaces don't restrict your heating to discrete heating levels (low or high). Instead, the furnace switches on at full speed until your home reaches the temperature you set for it. After that, the modulating furnace keeps turning off and on to maintain the temperature.

Here are the benefits of modulating furnaces:

  • They are energy efficient.
  • They can maintain heating at precise temperatures.

Here are the disadvantages of modulating furnaces:

  • They have high upfront costs.
  • They can be noisy since they have to switch on and off all the time.
  • They are more likely to break down than simpler types of furnaces.

Note, however, that the make and model of a furnace will determine its exact noise levels or upfront cost. Consult an HVAC contractor with your needs so they can help you choose the best furnace for your situation.