1-Stage vs 2-Stage Furnace – Pros And Cons

What’s the difference between a 1-stage vs 2-stage furnace? If you’re a homeowner, it’s good for you to know the advantages and disadvantages of each system. That’s because eventually, you need to replace the furnace you have.

The difference between 1-stage and 2-stage furnaces is in how the two operate. One-stage furnaces operate at 100% power when running, whereas two-stage furnaces constantly operate at 60-70% power, only increasing to 100% operating power when signaled by an extreme shift in indoor temperature.

Although this is the major operative distinction between one-stage and two-stage furnaces, there are certainly more relevant differences between the two central heating systems.

Continue reading to learn more about one-stage and two-stage furnaces, the differences between the two, and the pros and cons of each central heating system.

What is a One-stage Furnace?

A one-stage furnace is the simplest central heating system installed in their home in the modern era.

It consists of a furnace, which produces heat, a series of pipes running through the home, and a gas valve that allows gas into the furnace to burn, producing the heat.

The ultimate operative difference between one-stage furnaces and two-stage furnaces is in the way the gas valve functions.

The gas valve of a one-stage furnace opens at 100% capacity when in operation, which means your furnace will burn at full power when in operation.

This will continue until your indoor temperature has reached the temperature set on your thermostat.

One-stage furnaces are often considered to be an outdated central heating system.

However, one-stage furnaces are still being manufactured and improved upon, so the system is still far from obsolete.

What is a Two-stage Furnace?

Similar to a one-stage furnace, a two-stage furnace uses a furnace as the heat provider for its entire system, made up of a system of pipes running through the house.

However, two-stage furnaces use different programming than one-stage furnaces, which allow its gas valves to allow gas into the furnace at two separate levels.

The first level is at about 60-70% capacity, which is what two-stage furnaces tend to run throughout the day.

Then, once the indoor temperature has shifted noticeably, which typically dictates a shift of over 2 degrees, the gas valve will open at 100% capacity.

This will allow the furnace to start burning at full power.

This means, if your two-stage furnace’s programming decides it is only moderately cold, then it will only operate at a low power level.

This is different than a one-stage furnace, which will operate at full power until it has heated your room to the desired temperature set on your thermostat. 

The Differences Between A 1-stage Vs 2-stage Furnace

As mentioned in the previous section, the major difference between one-stage and two-stage furnaces has to do with how the gas valve of each system functions.

Although this is the main functional difference between the two furnaces, there are plenty of other differences caused by this major difference.

One-stage and two-stage furnaces function slightly differently, but there are also a few other key differences. 

Here is a list of some of the differences between one-stage and two-stage furnaces:

• Energy Efficiency
• Installation Cost
• Repair Rate

Now, let’s take a look at how one-stage and two-stage furnaces compare against each other in reference to these three differences.

Central Heating System	Total Cost of Installation	Total Lifespan Durability	AFUE (Annual Fuel Utilization Efficiency)
One-stage Furnace	$2,000-$3,500	15-30 years	90-95%
Two-stage Furnace	$2,500-$4,000	15-30 years	95-97%

These statistics were compiled from information provided on PickHVAC.

As is evident from the table, one-stage furnaces are the cheaper option in regard to installation costs.

However, when looking at energy efficiency, two-stage furnaces tend to perform better.

This means that two-stage furnaces may save you more money over time on your utility bill. 

One area in which one-stage furnaces and two-stage furnaces are quite similar is in their durability.

As one-stage and two-stage furnaces are fairly similar systems, they tend to last around the same amount of time.

Some homeowners swear that two-stage furnaces break down faster than one-stage furnaces. However, there is no evidence or statistic to back up this hypothesis.

We’re not done yet. There are some more tangible differences in how a one-stage furnace runs vs. a two-stage furnace.

These are differences that you’ll notice more frequently in your home. 

Here is a list of some other areas in which one-stage and two-stage furnaces differ:

• Noise
• Air Quality
• Temperature Consistency

Read: What affects indoor air quality?

Now, let’s take a look at these differences between one-stage and two-stage furnaces by comparing and contrasting the pros and cons of each central heating system.

The Pros and Cons of Two-stage Furnaces

Many contractors and homeowners have made the switch over to two-stage furnaces, citing functional and financial improvements.

This central heating system may be the popular choice, but it is important to note both the advantages and disadvantages inherent in two-stage furnaces.

Up next, we’ll take a closer look at the pros and cons of two-stage furnaces.

For a deeper dive, read: The Pros and Cons of Two-Stage Furnaces

Pros

There are a few advantages to having a two-stage furnace controlling your home. Here is a list of the advantages associated with two-stage furnaces:

• Steadier Indoor Temperature: Two-stage furnaces work by constantly operating at a low power level, which means that less cool air is being pushed through the ducts in your home. As a result, temperature swings greater than two degrees are uncommon, and your home will heat up faster than it will with a one-stage furnace.
• Improved Air Quality: Two-stage furnaces are constantly running, which means that they are constantly circulating the air in your home. This runs the air through the air filter more often, removing more airborne contaminants and leading to cleaner air.
• Lower Energy Use and Cost to Operate: Two-stage furnaces exert less effort to achieve the desired temperature on the thermostat, resulting in lower energy usage. This can end up being a noticeable amount saved on your monthly gas bill.
• Less Noise: One of the knocks against one-stage furnaces is that, as they only operate at 100% power, they simply make too much noise. As two-stage furnaces often run on less power, they tend to make less noise. However, both still make the same amount of noise at full power.

Cons

But of course, there are some very noticeable downfalls to two-stage furnaces. Here is a list of the disadvantages associated with two-stage furnaces:

• Greater Installation Costs: Although two-stage furnaces are not much more expensive to install than one-stage furnaces, they are still technically more expensive and might turn off prospective buyers as a result. One-stage furnaces generally cost between $550 and $1,700, whereas two-stage furnaces generally cost between $675 and $1,950.
• Greater Repair Costs: Although there is no conclusive evidence, two-stage furnaces are reputed to be more prone to breakdowns. This is rumored to be caused by their constant operation. Additionally, two-stage furnace repairs generally cost more, which means you will be paying a greater amount to maintain your central heating system more often.

Read: The Disadvantages of Two-Stage Furnaces

The Pros and Cons of One-stage Furnaces

Although a slightly outdated method for heating larger homes, the one-stage furnace is still a very effective method for heating smaller, one-story homes.

Let’s take a closer look at the advantages and disadvantages associated with one-stage furnaces.

Pros

Cost effectiveness is one of the major pros in owning a one-stage furnace. Here is a list of the advantages associated with those: 

• Cheaper Option: One-stage furnaces are far and away the cheapest central heating system installed in your home. One-stage furnaces generally cost between $550 and $1,700, coming to a total of $2,000 to $3,500 when including installation costs.
• Lower Repair Costs: In addition to the relatively low installation costs for a one-stage furnace, the repair costs for a one-stage furnace are equally low. One-stage furnaces are also generally found to be less likely to break down. Thus, you are paying less money per repair for more infrequent repairs with one-stage furnaces.

Cons

On the other side, there are a couple of major cons to consider. Here is a list of the disadvantages associated with one-stage furnaces.

• Energy Waster: As one-stage furnaces are constantly working at 100% power when on to achieve the desired temperature on your thermostat, they can often rack up expensive utility bills.
• Insufficient Central Heating System for Larger Homes: Part of this expensive cost of use is due to their inefficiency in heating up larger, two-story homes. One-stage furnaces can often leave cold spots throughout a house but will shut off once they reach the desired temperature in other pockets of the house.

Final Thoughts

Now you know a bit more about a 1-stage vs 2-stage furnace, the differences between the two, and the pros and cons of each central heating system.

Ultimately, the choice between the two will be determined by your own personal situation. Though the net advantages of a two-stage system are apparent, the up-front costs may be a hindrance for many folks.

But at least you are now armed with some useful knowledge that will help you make that decision more confidently, should the need arise.