What Is a Modulating Furnace?

HVAC efficiency is one of those things you might not consider all that much until it impacts you directly. Anyone who's paying the utility bill on a residence knows that efficiency can make a big difference to the budget over time. If you're wondering how you might reduce the cost of heating your home, the answer might be a modulating furnace.

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How Does a Modulating Furnace Work?

A modulating furnace includes a gas valve that modulates how much fuel is burned at any given time. Typically, this functionality is paired with a variable-speed blower. Together, these components work to control temperature increases incrementally to support optimal efficiency.

What Is a Single-Stage Furnace?

To best understand how a modulating furnace works and why it's more efficient than other options, it helps to understand what a single-stage furnace is. A single-stage furnace only runs at one level, and it's either on, or it's off.

A two-stage furnace, however, has several levels. When it's on, it operates at low or high, providing a bit more control and efficiency in the heating process. For example, in milder weather, a two-stage system runs at the lower level, providing sufficient heat to the home without overdrawing power. It only switches to the higher level when it needs to do so to keep up with the climate.

What Is a Fully Modulating Furnace?

A fully modulating furnace takes the two-stage or multi-stage concept to a new level. It can adjust output incrementally, making it easier to get to a desired temperature in a room or home.

What Is the Efficiency of a Modulating Furnace?

The efficiency of furnaces is measured in Annual Fuel Utilization Efficiency, or AFUE. This measures what percent of every dollar spent on fuel is actually converted to heat for the home.

Modulating furnaces have an average AFUE of 96% to 98%. That means almost 100% conversion of cost into heat. Compare that to the average AFUE for single-stage systems, which is 80%, and you can see how a modulating furnace could result in a lot of savings over time.

Does a Modulating Furnace Require a Special Thermostat?

Yes, you need a specific type of thermostat for modulating furnaces. This is because the thermostat must be able to communicate with the rest of the system to help control the incremental changes in heating. If you have a basic on/off thermostat, it may not work with a modulating furnace, or you may not get the full benefits of the modulating system.

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Is It Worth Getting a Modulating Furnace?

Homeowners considering this upgrade may wonder if a modulating furnace is worth it. That's a good question to ask because these units do tend to cost more than single-stage or multi-stage options.

To determine if a modulating variable speed furnace might be good for your home, factor in:

• The increased efficiency.

  Single-speed systems run at 100% the entire time they're on. Modulating furnaces run at varying levels depending on the heating needs at any given time.

• Long-term cost savings.

  You can do some back-of-the-napkin math to estimate how much you'll save on heating bills with a modulating furnace. Consider whether the unit will pay for itself during its lifetime based on how warm your family likes to keep your home.

• Better temperature control.

  Modulating furnace control offers more flexibility in managing the temperature of your rooms, which may result in better comfort for your family.

• Potentially better air quality.

  Because modulating furnaces operate a lot of the time on lower settings, they aren't burning as much fuel. This can lead to reduced byproducts entering your home, ensuring better air quality.

If you're not sure if a modulating furnace is right for you, consult an HVAC technician about your options. They can help you understand what benefits you might see compared to your experience with your current furnace. You can also review a quote for a modulating furnace installation so you can understand the long-term cost and savings implications.