Two-stage Furnace – What Are pros And Cons?

If you are a homeowner or currently in the process of becoming one, then the chances are that you have been given the spiel on one-stage versus two-stage furnaces.

There will come a time in every homeowner’s life in which the air conditioning and furnace of the home will need to be replaced. Then, it will matter whether or not you listened to the one or two-stage furnace spiel.

Two-stage furnaces possess two levels of heating output, the first stage running between 70-80% of the furnace’s rated capacity, with the second stage being activated only in necessary conditions. Two-stage furnaces are generally effective in balancing the temperature swings in a household and lowering energy use.

Although two-stage furnaces sound like the superior choice when comparing them to one-stage furnaces, there are plenty of pros and cons associated with both options.

Continue reading to learn more about one-stage and two-stage furnaces, the disadvantages and advantages of both options, and which option is right for you.

What is a Two-stage Furnace?

Every home built with a central heating system features either a furnace, boiler, or some other method for providing heat throughout the house.

Many houses, particularly units built before the 21st century, use a furnace as the heat provider for their central heating system.

You will find two major types of furnaces and one other central heating system in any given household, a one-stage furnace, a two-stage furnace, and variable capacity gas valves sometimes included within an HVAC system. 

  • One-stage Furnace
  • Two-stage Furnace
  • Variable Capacity Gas Valves

An HVAC is a central system that includes heating, ventilation, and air conditioning. It is often more complex and expensive to install, but it is the most effective and saves the most energy.

A one-stage furnace works by running at full power while turned on to reach the desired temperature set on one’s thermostat.

A two-stage furnace works by constantly operating at a low power setting, roughly 70% of full power, and switching over to full power when needed. 

This switch occurs when the room temperature fluctuates two degrees or more below the temperature set on the thermostat.

A standard HVAC system features three units, a heating unit, ventilator unit, and an air conditioning unit, that work together to produce each unit’s specific function. An HVAC heats a home through several rotating coils that heat the air being blown into the room by the HVAC’s blower.

How Does a Two-stage Furnace Work?

Two-stage furnace functions like a one-stage furnace, using a furnace as the heat provider for the entire system, made up of a system of tubes throughout the house. 

However, two-stage furnaces use different programming than one-stage furnaces. With a two-stage furnace, the control board reacts to your house’s internal temperature in partial and full measures.

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 Pros and Cons of Two-stage Furnaces

Two-stage furnaces have become more commonplace in households in recent history, starting at the turn of the century. This is partially due to the fact that more contractors’ salesmen have pitched the system over one-stage systems.

One-stage furnaces are also easy to find, and parts for repairs are readily available.

Although this central heating system may be the popular choice, it certainly features its share of advantages and disadvantages. 

But before you can decide which is the best option for your home, let’s investigate the advantages and disadvantages. 

Pros

Here is a list of the advantages associated with two-stage furnaces.

  • More Comfortable, Steady 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.
  • Lower Energy Use and Cost to Operate: This also results in lower energy use as two-stage furnaces work less hard to achieve the desired temperature on the thermostat. This can end up being a noticeable amount saved on your utility bill.

Cons

A two-stage furnace comes with its own set of disadvantages. Up next, the cons.

  • 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: Additionally, two-stage furnaces also feature greater repair costs. This is part of why contactors’ salesmen will typically try to upsell two-stage furnaces over one-stage furnaces.

The Pros and Cons of One-stage Furnaces

Although one-stage furnaces are a slightly outdated method of heating larger homes, they are still very effective at heating smaller or one-story homes.

Let’s look at some of the other advantages and some of the disadvantages associated with One-stage furnaces.

Pros

Let’s take a look at the positives of one-stage furnaces.

  • The Cheapest Option: One-stage furnaces are easily the cheapest central heating system to install in your home. They generally cost between $550 and $1,700 to install, and their installation is quite a simple process.
  • Repair Costs Are Low: In addition to the relatively low installation costs for a one-stage furnace, the repair costs for a one-stage furnace are equally low. It is also fairly simple to repair a one-stage furnace.

Cons

Here is a list of the disadvantages associated with one-stage furnaces.

  • Wastes Energy: As one-stage furnaces are constantly working at 100% power to achieve the desired temperature on your thermostat, they can often rack up expensive utility bills.
  • Cannot Sufficiently Heat Up Larger, Two-Story 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 reach the desired thermostat temperature and shut off. 

The Pros and Cons of HVAC Central Heating Systems

Generally considered the most modern central heating system of these three options, HVAC systems are quickly becoming the norm in larger, more upscale houses. 

Despite all of this popularity, HVAC systems are certainly not perfect. Let’s take a look at the pros and cons associated with HVAC central heating systems.

Pros

Here is a list of the advantages associated with HVAC central heating systems.

  • Most Effective at Maintaining Steady, Comfortable Temperatures: HVAC systems are the best system for providing steady, comfortable temperatures throughout a household. Many HVAC systems are even designed to regulate humidity and air distribution in addition to temperature regulation.
  • Most Conservational Central Heating System: When operating effectively, HVAC systems are also the most conservational and inexpensive central heating system while in use. HVAC systems use 66% less electricity than one-stage furnaces and can save a fortune on utility bills.

Cons

Here is a list of the disadvantages associated with HVAC central heating systems.

  • Most Expensive Option to Install and Repair: Although the cheapest option for central heating while in use, HVAC systems are the most expensive option to install. HVAC systems generally cost between $4,000 and $7,000 to install. Additionally, they are also more expensive to repair.
  • Breaks Down More Frequently: HVAC systems are relatively new technology and, as a result, break down more frequently. HVAC systems are fairly complex and will likely cost more of your time and money to repair. 

Is a Two-stage Furnace Right for You?

Now that we have gone over several central heating systems and outlined the pros and cons.

Hopefully, this will help you decide which option to install in your home. It is time to decide which central heating system is right for you.

Let’s take a closer look at two-stage furnaces. Two-stage furnaces stack up well against one-stage furnaces regarding energy efficiency and low operative costs.

Still, the central heating system is generally not quite as effective as HVAC systems in heating throughout larger homes, and it costs more to install than a one-stage furnace.

Here is a table that compares the costs and efficacy of two-stage furnaces versus one-stage furnaces and HVAC systems.

Central Heating SystemInstallation CostDurabilityAFUE (Annual Fuel Utilization Efficiency)
One-stage Furnace$550-$1,70015-30 years90-95%
Two-stage Furnace$675-$1,95015-30 years95-97%
HVAC System$4,000-$7,00010-20 years98+%

This data was compiled from Kompareit, Comfort Pro, and PickHVAC.

Final Thoughts

At the end of this article, you should have a general idea of what a two-stage furnace is, how a two-stage furnace operates, and what the pros and cons of a two-stage furnace are when compared to one-stage furnaces and HVAC systems.

Ultimately, two-stage furnaces are a great option for those living in colder climates looking to save money on their utility bills.