Efficiency and Benefits of Two-Stage Furnace

One-stage furnaces are still being manufactured and improved upon today, however, many still consider the system archaic and for the most part, they are right. A one-stage furnace, especially an older model comes with far more cons than pros.

According to the U.S department of energy, space heating is the largest energy expense in the average U.S. home, accounting for about 45% of energy bills. And, an older one-stage model furnace consumes far more energy due to its operation mode.

While a two-stage furnace has the obvious energy-saving benefit, it has far more advantages. For example, a two-stage furnace is quieter, offers better indoor air quality, and is far more efficient. While it is more expensive to set up, in the long run, a two-stage furnace would prove to be the better financial choice.

In this article, you’ll learn the benefits and disadvantages of single and two-stage furnaces. You’ll also discover how the two-stage furnace compares to a single-stage furnace in operation and if it’s worth your investment. Let’s get right into it.

What is a two-stage furnace?

A two-stage furnace has two different heat output levels— for cold and milder periods. As a result, the furnace mostly runs low power, conserving energy and controlling the home’s temperature. In addition, they have a consistent heat distribution that delivers heat evenly in the home. This way, there are no cold spots, and everywhere in the home is at a uniform temperature level. 

Also, two-stage furnaces offer long-lasting power-saving benefits because it operates at a lower capacity. As a result, it burns less fuel and helps you save a lot of energy. It can also operate at a high capacity based on your settings and outdoor temperature.

Two-stage furnaces are excellent for families living in large, or multiple-story homes. It may also be an effective replacement if your current single-stage furnace does not meet your heating needs. It’s best to consider your budget, the home’s size, and layout, and your specific heating expectations to know if a two-stage furnace is your home’s best choice. 

Benefits of a two-stage furnace 

Two-stage furnace offers several benefits. Understanding its perks will help you decide if it’s the right choice. Let’s take a look at some of its significant advantages. 

More efficient 

If you want to reduce your utility bills, a two-stage furnace can help. Although it costs more than regular furnaces, a two-stage furnace serves lasting cost-saving benefits. Since it has a dual-stage burner, it can regulate its heating temperature based on varying degrees. For example, if the home’s temperature is several degrees low, the two-stage burner will increase its intensity, evenly distributing heat across the rooms. 

Also, the two-stage furnace switches to low-heat distribution mode if the room is at normal temperature. It customizes its heating power to the room’s temperature, ensuring the home is always well-heated. As a result of its self-regulatory function, a two-stage furnace reduces your utility bills and helps save on energy. 

On the other hand, a single-stage furnace has a single power mode that makes it less efficient. It operates at its full power whenever it works, so there’s no way to control power consumption. 

Since it works at optimal power mode, some areas of your home warm up faster while others stay cold. Finally, in most cases, the furnace shuts down completely before the heat is fully distributed across the home. So, single-stage furnaces aren’t the best option for large homes and those looking to cut down on utility bills. 

Quieter operations 

Two-stage furnaces operate more quietly than one-stage furnaces. This is because the two-stage furnace works at a lower speed and cycles less, reducing the noise it makes. Contrarily, one-stage furnaces cycle faster and operate at full speed. As a result, the air travels at high velocity, increasing its sound. 

Besides noise reduction, a two-stage less cycling operation means less stress on its engines. Consequently, it minimizes breakdown and prolongs its lifespan. So, a two-stage furnace is an excellent option for a quieter environment. It’s also a good choice for increasing the system’s longevity and reducing maintenance costs. 

More consistent temperature

Consistent heat distribution is a top perk for homes with a two-stage heating system. Single-stage furnaces have no regulatory function, so they operate at full blast when they are on. As a result, some parts of your home become overheated while others struggle to warm. This inconsistency makes a single-stage furnace less functional for many homes.

A two-paced furnace distributes heat evenly, ensuring every part of your home is warmed up at equal temperatures. Therefore, it prevents temperature fluctuations and allows every part of your room to benefit from consistent heating. 

Cheaper to run 

Typically, a two-stage furnace is costlier than a single-stage furnace. However, it’s cost-efficient in the long run. It offers up to 20 to 25 percent energy cost savings advantage, making it cheaper to run long term. 

Additionally, two-stage furnaces offer a long-lasting advantage over single-stage models. Since they are under less stress, they don’t break down easily, so there is minimal need for regular maintenance. Their durability also means you won’t need to replace them quickly, enabling you to maximize cost.

How does a two-stage furnace work?

Single-stage furnaces and two-stage furnaces have valves that control them. For example, a single-stage furnace has two positions, open and closed. When the valve is opened, gas goes through the valve, ignites, and burns inside the furnace’s burner section. Afterward, the heated gases travel to the heat exchanger to heat your home. 

Unlike single-stage furnaces, two-stage furnaces valves operate in three positions—open, partially open, and closed. When working, the valve switches to any of these two open positions. As a result, it can operate in a full-power mode or a low-power mode that reduces the generated heat to about 60 to 65 percent. 

You can maintain your two-stage furnace by servicing it once a year. Dirt can affect the different components of your two-stage furnace and slow down operations and efficiency, so clean it regularly.  

A crack in the heat exchanger can cause the flame to come out of the burner opening, resulting in a fire. So, it’s good to check the heat exchanger regularly for cracks or damage. Additionally, your system’s efficiency reduces when the burner is clogged. So, check, clean, and replace your burner filter often.

Other maintenance practices involve checking if your heating burners are damaged or dirty and if the vents are blocked. Regular inspection and cleaning will keep your two-stage furnace in the best condition for lasting use.

What is a one-stage furnace? 

Unlike a two-stage furnace, a single-stage furnace works at one capacity – Full.  This means the room’s average and the outdoor temperature doesn’t influence how it works. 

Conversely, a two-stage furnace has a two-stage gas valve with a variable-speed blower motor. So, the two-stage furnace can run at a lower setting during normal temperatures and works at high intensity at low temperatures. A single-stage furnace works the same way, despite the cold that may be present outside.

Here are notable key differences: 

  • A single-stage furnace has a single-speed blower motor and a fixed valve, while a two-stage notable speed motor has a variable-speed blower motor. 
  • Single-stage furnaces cost lesser than two-paced furnaces. However, two-paced furnaces are cheaper to run due to their high efficiency. 
  • Although single-paced furnaces are less complicated, they attract high maintenance costs because they may break down easily from the full power-mode operation. 
  • A single-stage furnace doesn’t offer consistent heating benefits. This is because it doesn’t distribute heat evenly across the home. Consequently, it leads to temperature fluctuations that may make some parts of the home uncomfortable. 

Benefits of a one-stage furnace

A one-stage furnace has certain advantages, making it a good choice for some homes. Let’s look at the most prominent benefits of one-stage furnaces below:

Less expensive 

Single-stage furnaces are cheaper than two-stage furnaces. Typically, two-stage furnaces cost about $500 more than single-stage furnaces. This means if a manufacturer sells a double-stage furnace for $4,200, a single-stage furnace would likely be sold for about $3 700. 

So, if you are looking for a furnace on a budget, a single-stage furnace is an excellent choice. However, although they are cheaper, they don’t provide low utility savings. 

Quick to heat

Single-stage furnacing has only one setting. So it’s either they are working at a 100% full blast mode or not working at all. The full force at which they work enables them to heat the home quickly. However, although they distribute heat poorly; users in smaller homes benefit from the instant warmth the furnace produces. 

Its ability to warm up the house quickly makes it an excellent choice for extremely cold weather. So, a single-stage furnace is right if you prefer quickly heating your home in very cold conditions. It’s also a perfect option to limit the heat to a specific place. 

Easy to operate 

A single-stage furnace is less complex to install, use and maintain. It has just two settings—off and on. It also has fewer parts that are easy to set up and fix. Its simplicity makes it easy to set up and shut down very straightforwardly. So, consider single-stage furnaces if you want a less complicated, easy-to-use heating system. 

How does a one-stage furnace work? 

The one-stage furnace is a basic central heating system with a furnace, pipes, and gas valve. The furnace supplies heat, and the valve transports the gas into the furnace, burning and generating heat across the home. 

One-stage furnace means that the furnace has a valve. The valve supplying the burner with gas consists of two settings, a full-power mode or no-work mode. They distribute the heat in the home at a single speed and an optimal capacity. 

The home’s thermostat demands heat, turning on the furnace at full power. It works at 100% mode till the thermostat shuts it off. The warmth spreads across the area with full force but not enough to distribute the heat entirely if it’s a large area. However, the maximum capacity at which it works makes it a quick, temporary fix for warmth in the home. 

While its full operation mode may be less efficient, it may be fine if you plan to move soon. So, it’s a good choice if you need a heating system while residing in a place temporarily. You can also purchase a single-stage furnace if you are trying to save till you can afford a two-stage furnace. 

A one-stage furnace works best with consistent maintenance. Since it has fewer parts, single-stage furnace maintenance is quite straightforward. First, check your thermostat regularly to see if it’s in the best condition. Next, clean the blower frequently to eliminate dirt, debris, and dust. Finally, check the filter system regularly to unclog dirt for effective filtering.

The best way to ensure your filter stays in good condition is to practice regular check-ups and maintenance. Doing this will help you identify damages early and make quick repairs. Consequently, you will save on high maintenance costs from major issues and ensure the smooth running of your single-stage furnace. 

Is a two-stage furnace worth the investment? 

A two-stage furnace is a worthwhile investment and is more efficient (than something like a single-stage AC unit) if you want to save on utility bills and enjoy consistent heating, even heat distribution, and durability. Although it is more expensive, it offers significant advantages over the single-stage furnace. 

While the one-stage furnace may be a good option for people seeking temporary use, or those who live in small houses, a two-stage furnace is a perfect choice for people with varying needs. 

You should opt for a two-stage furnace if: 

  • You live in a large home: A two-stage furnace is right for you if you need the heat to circulate across a large area. While a single-stage furnace focuses the heat in a particular place, a one-stage furnace targets the heat in different areas of the house.
  • You want excellent air quality: When a one-stage furnace operates; it warms up the home rapidly and goes off. As a result, the air doesn’t circulate in the home effectively. Also, it doesn’t purify the air through the filter, causing poor air quality. On the other hand, a two-stage furnace can operate at a low mode, enabling the air to pass through the air filter, removing pollutants, and enhancing air quality. 
  • You want a quiet home: If you want to avoid the distraction from the noise the single-stage furnace makes, opt for a two-stage furnace. It cycles less and works at a low speed, decreasing the noise and creating a quiet, peaceful atmosphere. 
  • You want to save on energy expenses: A two-stage furnace reduces your utility bill. In addition, it doesn’t work at its maximum capacity unless necessary, reducing its power usage. So, in the long run, you will cut energy savings costs compared to a single-stage furnace that works at full capacity. 

If you fall into the categories above, the best choice of furnace to buy is the two-stage furnace. A highly efficient, durable furnace will adequately meet your heating needs and give you the best value for your money. 


The most suitable heating system is based on your unique expectations. First, think about how efficient you want your heating system to be.

Next, consider the size of the rooms, local climate, and insulation level. Finally, evaluate the cost and the amount you are willing to spend. Then, compare prices, maintenance costs, and utility expenses. Weighing these factors will point you toward the most appropriate furnace system to buy.