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Single‐Stage, Two‐Stage, or Modulating Furnace?

Efficiency HVAC

I spent some time this past week working with a customer to help them understand the difference between two different furnaces. What I learned from the experience is that I needed to do a better job of describing the various value propositions for the different types.

So, let’s break down the different types of furnaces while keeping it very simple. If you still have questions, feel free to reach out to us. We’d love to help.

Many older furnaces and lower-cost newer furnaces are single‐stage (or single‐speed) heating systems. This means that they are either on or off, and when they are on, they put out heat at a constant level. To keep the house at a constant temperature, a single‐speed furnace must cycle on and off frequently. How do you know if you have a single‐speed furnace? If you can tell that the furnace is running by the noise it makes, you most likely have a single‐speed furnace.

Newer furnaces, by contrast, are generally Two‐Stage that can produce heat at two rates. Two‐Stage furnaces are more energy-efficient than single‐stage furnaces because single-stage furnaces must constantly turn on and off.

These newer furnaces will help keep the temperature more constant (better comfort) by running at a slower speed. This slower speed will also be less noisy.

A Modulating furnace is even more efficient than a Two‐Stage furnace. A modulating system pairs a variable‐speed blower with a computer‐controlled gas valve. These systems can run at several different levels, adjusting automatically to maintain a constant temperature (highest comfort). Because they adjust energy use based on need, they’re the most efficient type of furnace, as well as the quietest. Modulating furnaces also make your air conditioner work better by staging the fan speed for better dehumidification, thus giving the homeowner the best possible comfort.

In addition to saving fuel, variable‐speed furnaces use less electricity to power the fan motor. According to the American Council for an Energy‐Efficient Economy, the amount of electricity used to run a furnace motor can be significant. Thus, a more efficient, variable‐speed fan motor can produce significant savings.

So whether you were looking at a Single-stage unit or going all out for comfort with a Modulating Furnace, you now know some of the furnace basics, giving you the power to make an informed decision that fits both your budget and comfort.

We would love to hear from you. Great companies want honest, compassionate feedback that helps them serve you better. Please tell us how we are doing and ask any question that you might want to be answered, reach out at AskFry@RELYonFRY.com

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Fry services and installs: Furnaces, Air Conditioners, Humidifiers, Dehumidifiers, Tank and Tankless hot water heaters and backup generators. We service Residential and Commercial customers.

At Fry, we are “A breath of fresh care”.

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