Two-stage vs. modulating furnace for Kansas City homes.

Wondering whether you should get a two-stage or modulating furnace for your home?

Well, here’s the good news: both are good choices for comfort and energy efficiency, and both are a step up from a single-stage (standard) furnace.

But if you’re stuck on which one to choose, it basically comes down to this: If you want to save money on equipment costs and are OK with mid-level comfort, go with a two-stage furnace.

On the other hand, if ultimate comfort is your #1 priority and money isn’t your biggest concern, you’ll want to go with a modulating furnace.

Want to know more details about two-stage and modulating furnaces? In this article, we’ll cover:

  • How each furnace works
  • The pros and cons of each
  • How to find the right furnace for your home

Let’s start with two-stage furnaces:

Two-Stage Furnaces

How they work

Imagine you’re buying a car, and you’re choosing between two different models. One model only has two speeds: 0 mph or 100 mph, with no speeds in between. The second car has three speeds: 0 mph, 60 mph and 100 mph.

The first car is like a standard furnace; it only turns ON and OFF. This makes it hard to heat rooms equally and causes a fairly large temperature fluctuation (5+ degrees) throughout your home. No matter how cold it is outside, this furnace will always run at 100% capacity when it is on.

However, the second car is like a two-stage furnace: it turns ON and OFF, but also has a LOW OUTPUT setting that runs around 65 – 68% of full capacity. Having these three positions allow the furnace to better regulate temperature, humidity and air distribution throughout your home.

Take a look at how a standard furnace compares with a two-stage furnace in terms of temperature swings:

During milder winter days, when you don’t need your furnace to be on full blast all day, a two-stage furnace can conserve energy and better regulate your home’s temperature. Studies have found that energy savings come when a two-stage furnace is paired with a BPM motor.

Two-stage furnace pros and cons

Two-stage furnaces are the most popular types of furnaces on the market today. Let’s look at why:


  • More even temperatures: During the furnace’s Low Output mode, which runs longer, temperatures with your home will remain more consistent.
  • Quieter operation: Two-stage furnaces run at Low Output most of the time, which reduces furnace noise, compared to running at full blast all of the time.
  • Enhanced air quality: Because a two-stage furnace can run more than a single-stage furnace, your air filter’s will be able to capture and remove more contaminants.
  • Better furnace efficiency: Two-stage furnaces burns less fuel than a standard furnace that always runs on full capacity.


  • More expensive than single-stage furnaces: They generally cost $500+ than single-stage furnaces.
  • Not as energy-efficient or comfort effective as modulating furnaces: Modulating furnaces provide the ultimate in both energy efficiency and comfort. Learn more about them below:

Modulating Furnaces

How they work

Going back to the car analogy, a modulating furnace functions the closest to a normal car. A normal car accelerates gradually from one speed to another, with speeds ranging from 0 mph to 100 mph, with all speeds in between.

When you first turn on a modulating furnace, it will seem like a standard single-stage furnace. It will start at maximum power, but then it will gradually decrease heating power as heat builds up in the home, which makes your home’s temperature feel consistent.

A modulating furnace has gas valves that reduce gas flow to the burners as the blower fan increases speed. This allows the furnace’s heating capacity to increase in small increments to maintain maximum heating efficiency. It also means you can preserve your home’s temperature to within about ½ degree of your thermostat’s set point.

The visual below shows how modulating furnaces are the best for maintaining home temperature:

Image source:


Modulating furnace pros and cons

Modulating furnaces provide maximum comfort and energy savings, but cost more upfront. Let’s look more at their pros and cons:


  • Maximum comfort: This is the #1 reason to get a modulating furnace. You’ll notice a marked difference with your home’s heating comfort because the furnace does not wait for room temperature to fall before kicking in. Your home won’t feel too cold or too hot, but just the right temperature.
  • Energy savings: Modulating furnaces rarely run the fan and gas burner at 100% full capacity together, which cuts down on the on/off cycling typical of a standard furnace. This makes modulating furnaces the most fuel-efficient models available.
  • Eco-friendly: Modulating furnaces are highly efficient (AFUE ratings are generally 95% to 98%), which makes them a green purchase.


  • Noise is not louder, but more frequent: At first, modulating furnaces may seem louder, but they’re actually not. Most people who are upgrading from single-stage furnaces are used to hearing silence when the furnace shuts off. Modulating furnaces run more frequently and will therefore produce more consistent noise, but it won’t be any louder than other furnaces.
  • Cost is higher than single or two-stage furnaces: You can estimate about $5,000 – $6,000 for a new 98% AFUE furnace installed.

Find the right furnace for you—contact an expert for advice

To find the right furnace for you, an expert will need perform a load calculation to determine the proper furnace type and sizing for your home. Your HVAC specialist will give you the best recommendation based on your budget and heating needs.

Contact us today for a free furnace recommendation. We’ve been serving the Kansas City Metro area since 1987.