Single vs. Two-Stage vs. Variable Capacity Furnaces: Which One Is Right for Your Home?

Winter is still a few weeks away, but many parts of Ontario including Hamilton and surrounding areas have already begun to experience lots of snow and frigid temperatures. While most dwellings are equipped with furnaces to keep our interiors toasty and warm, not all furnaces are created equal. As a homeowner, you may have a single-stage, two-stage, or variable capacity furnace to heat your home.

What’s the difference between a single stage furnace, a two-stage furnace, and a variable furnace? How do you know which one is more energy- and cost-efficient for your home?

Keep reading for cost, performance, and compatibility comparisons between all three types of furnaces. Just be aware that these varieties only apply to gas furnaces, so if you have an oil or electric unit, then this might not apply to you.

What Is a Single-Stage Furnace?

Single-stage furnaces are designed to heat your home during the absolute coldest months of the year in your region. As a result, they typically run at the highest possible capacity whenever they’re in operation, regardless of what the temperature and whether is like outside. The reason they’re called single-stage furnaces is because they only have one setting when in operation. One of the few benefits of a single-stage furnace is that the upfront cost is comparably lower than two-stage or variable furnaces.

Since single stage furnaces only have one setting, they don’t distribute heat evenly throughout your home which means that you’ll notice a lot of cold and very warm spots throughout your home. Not only does this impact your monthly energy bills because your furnace is constantly running at full capacity, but it also affects your comfort level throughout your home.

Single-stage furnaces are now becoming obsolete and the government is requiring homeowners to install furnaces with 95% efficiency or higher.

What Is a Two-Stage Furnace?

Two-stage furnaces are the opposite of their single-stage counterparts in that they feature two settings instead of one. That means they don’t automatically always operate at full capacity. As the name indicates, two-stage furnaces have two heating outputs: high and low. The high setting is appropriate for extremely cold temperatures and climates, whereas the low setting is used for milder temperatures, such as early autumn days.

Considering the two-stage heating system typically runs at the lower capacity of about 70-80% in most households—depending on how cold it gets in your geographical region, of course—it’s usually classified as the more cost- and energy-efficient option of the two. The low capacity allows many homeowners to keep their two-stage furnaces running for a longer period (usually early October-late April) and they also provide more even heat distribution than single-stage furnaces. Depending on your needs, the benefits of a two-stage furnace outweigh those of a single-stage furnace.

What Is a Variable Capacity Furnace?

A variable capacity (also known as variable speed) furnace is arguably the most versatile option out of the three. Variable capacity furnaces feature a strong indoor blower motor which can operate at multiple settings and be adjusted according to your specific needs rather than only producing single or dual speeds. Therefore, variable capacity furnaces can more accurately control heat and distribute it evenly throughout your home.

Variable capacity furnaces also have the ability to automatically adjust the blower settings based on certain factors in your home that may restrict air flow, including dirty filters, the location of your furnace, the design of your ductwork, etc.

Not only do variable capacity furnaces provide a more consistent temperature throughout your home to eliminate cold spots and automatically adjust according to the temperature of the house, but the blower motor will still function even when the furnace itself is turned off. Effectively, what this does is it continues to improve the air quality and circulate clean air throughout your home, which reduces the amount of dust and allergens that you and your family breathe in.

Here’s a brief comparison chart of the three furnace options:

Type of Furnace Cost Efficiency Maintenance Repair Cost
Single-stage furnace From $2,800 to $4,000 pending BTU input and difficulty of job Not very efficient



Annually Relatively low due to less efficiency



Two-stage furnace From $3,000 to $6,000 pending BTU input and difficulty of job



About 95-97% efficient depending on the capacity Annually More expensive than single-stage furnaces due to more intricate parts
Variable capacity furnace From $3,500 to $8,000 pending BTU input and difficulty of job 95-98% efficient Annually Costs the most due to the high-tech parts

Two-Stage and Variable Furnaces Vs. Single-Stage Furnaces? Which One is Better?

The answer to this question is simple. Single-stage furnaces have a much lower upfront cost—and that’s pretty much where the advantages end.

Single-stage furnaces are only ideal for homeowners who are looking to save money on purchasing a furnace or who aren’t planning on spending much time in their homes. So, is a single-stage furnace a good investment? That depends on what you’re looking for and what you can afford to spend.

You’re better off spending a little extra money on the upfront and installation costs of purchasing a two-stage or variable furnace to heat your home. Two-stage and variable capacity furnaces have the capability of increasing your comfort level throughout your home by distributing the heat as evenly as possible throughout every room and you can adjust the temperature according to your preferences.

Between the low-end single-stage furnace and the high-end variable capacity furnace, a two-stage furnace is a perfectly moderate compromise in that it gives you the best of both worlds.

Contact MDM Mechanical for Furnace Installation, Maintenance, and Repairs

MDM Mechanical is a family-owned and operated furnace installation, maintenance, and repair company that provides high-quality heating and cooling services throughout Hamilton and surrounding areas. We’re committed to providing our customers with the best possible service according to their needs. Contact us today to book a consultation with one of our specialists.


About Michael Mead

Michael Mead was born and raised in London, Ontario. He spent 5 years in Calgary, Alberta – and furthered his education in Natural Gas. If Michael isn’t working, he is at home with his son and wife or cooking for a large group of family and friends. Michael is extremely passionate about his business, and is constantly looking for ways to better himself as an employer.

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