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Furnace Types Explained – Single Stage vs. Dual Stage vs. Modulating

We examine the different types of forced-air furnace, and compare the difference between single stage, dual stage, variable-speed, and modulating furnaces.


What is a single-stage furnace?

A single-stage furnace has two settings: on and off, that is, your furnace is either running at maximum capacity or not at all.


This option, because it is an older style and less energy efficient, will cost you less to purchase outright.


Single-stage furnaces do not efficiently use energy and your bills may remain the same, or climb higher. These types of furnaces are also less environmentally friendly their modern counterparts.

You may find warm or cold spots in certain areas of your home and your home temperature may spike and drop over time. Single-stage home heating systems can be noisy, when they turn on and off or even during regular operation.

What home is it best suited for?

If you’re in your home for the short term, it may be worth considering a single-stage furnace, since you will not be there long enough to reap the rewards of lower energy bills. If you live in a bungalow or other type of small, one level house, a single-stage furnace may be enough to heat the space evenly.

Is a single-stage furnace worth it?

If your priority is to save on the initial purchase of your furnace, a single-stage may be for you. But you should really only buy a single stage furnace if you absolutely can’t spare a few hundred dollars extra for a better model, like the ones below.


What is a dual-stage furnace?

Within the “on” setting of a dual-stage furnace, there is a low and a high setting. Generally, your furnace will run on the low setting. If there is a sudden change, like an influx of cold weather, the furnace will kick into high gear.


Dual-stage furnaces deliver a more consistent heat to your home and are more responsive to weather fluctuations, resulting in less drastic temperature changes inside. They are more efficient energy-wise than a single-stage furnace, the outcome of which is lower energy bills.

Models are designed to operate more quietly and because the furnace is not switching on and off over the course of the day, they are less disruptive. A high-efficiency furnace can also be eligible for a government rebate.

Check out our Current Heating & Cooling Deals and Promotions for current furnace deals and discounts in your area.


Dual stage furnaces are typically a bit more expensive than single stage models ($250 – $600 more on average), but it’s often a worthwhile investment to achieve more consistent and comfortable heating, and better energy-efficiency.

However keep in mind the the furnace is only part of the equation. If your home has poor insulation and old, drafty windows, a new high-efficiency natural gas or propane furnace won’t fix everything!

What home is it best suited for?

If your home has multiple levels, has a tendency towards cold and hot spots or if you live in an area in which you experience drastic temperature drops or changes, a dual-stage heating system will keep you cozy, consistently.

Given a typical cost difference of only a few hundred dollars, dual stage furnaces are a good option for pretty much any homeowner who can afford it.

Is a dual-stage furnace worth it?

A dual-stage will cost you slightly more in the beginning, but with lower energy bills and improved comfort, it’s a small price to pay and worth “splurging” for.


What is a variable or multi-speed furnace?

A variable or multi-speed furnace monitors the temperature of your home and then adjusts the speed of the blower motor, sometimes referred to as an ECM motor, in very small increments. This increased precision results in a home that is more consistently heated, both in different areas of the home and over time.


A variable or multi-speed furnace offers a higher level of efficiency, because the system does not have to run at full capacity in order to reach the set temperature. If your furnace has an ECM motor, and is used continuously, energy consumption can be reduced by 70%. Consistent airflow also means a more regulated temperature and ongoing air filtration. Because your furnace does not abruptly stop and start up, these units are much quieter.


Initial investment costs are higher than other less advanced home heating systems.

What home is it best suited for?

It is worth considering how long you will be in your home. You will initially spend more money on your furnace and you want to make sure that you will be there long enough to recoup some of those costs through lower energy bills. Because variable-speed furnaces tend to be more energy-efficient and may be ENERGY STAR® certified, you may qualify for rebates to help offset some of the cost. Be sure to ask your local HVAC supplier for details!

Is a variable/multi-speed furnace worth it?

If you’re planning on staying in your home for at least 5 years, it’s worth considering a significant investment in your home heating that, with proper installation and maintenance, will increase your comfort, reduce your energy bills and last for the long haul.


What is a modulating furnace?

A modulating home heating system has a burner that adjusts the amount of fuel burned incrementally in order to maintain a consistent temperature. A furnace can have both a variable/multi-speed blower and a modulating burner, offering the most precise and consistent heating out there.


The temperature is more consistent throughout your home with this option, including in different areas and over the course of time, even if the weather outside changes rapidly. A modulating furnace is highly energy efficient, since it is regularly monitoring and adjusting the amount of fuel burned, minimizing waste and environmental impact.


A modulating furnace will likely be more expensive, and the may not be a huge difference in overall performance and efficiency.

What home is it best suited for?

If you plan to stay in your home for the foreseeable future, consider investing in a high-efficiency furnace. The unit will cost more on the outset, but costs can be lessened through government rebates and savings on energy bills. Because modulating furnaces tend to be more energy-efficient and may be ENERGY STAR® certified, you may qualify for rebates to help offset some of the cost. Be sure to ask your local HVAC supplier for details!

Is a modulating furnace worth it?

If you’re willing to spend a bit extra to get the best, and achieving maximum heating comfort and efficiency is important to you, a modulating furnace is a good option. If you’re looking for something a bit more basic or your budget is more limited, a modulating furnace probably isn’t essential.


So, what should you buy?

To recap, here are some general recommendations on the different furnace types:

  • Single Stage: Buy this only if you really only want or can afford the most basic and cheapest furnace, otherwise get at least a dual stage model.
  • Dual Stage: A good step up and worth the investment for homeowners looking for a bit better performance and efficiency.
  • Variable Speed & Modulating: If you a bit of a higher budget and want improved energy-efficiency, better home comfort with quieter operation, and want to potentially qualify for rebates with an ENERGY STAR certified heating system, these features are worth considering.

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