The Difference Between One-Stage and Two-Stage Furnaces

If you’ve been shopping around for a new furnace, chances are you’ve encountered both one-stage and two-stage furnaces. As you can probably tell, not all furnaces are created equal, with some two-stage systems offering a superior performance that others simply can’t match. If you’re wondering how exactly they differ from your average one-stage system and whether or not they’re worth the cost, you’re not alone. The answer typically depends on a number of factors, however. There are many benefits to the use of a two-stage furnace and taking your needs, regional temperature and budget into consideration can help you determine if it’s the right choice for you.


What Is a Two-Stage Furnace?

To understand what makes a two-stage furnace unique, it’s important to know how a one-stage furnace works. In this case, the “one” actually refers to the valve that controls the burner section inside the furnace. Apart from being “closed”, the valve only has one position, which is “open”, and this allows fuel, typically natural gas or propane, to travel to the pilot light to ignite. The heat created in the burner section then heats up the heat exchanger where the air in your home is heated. In the “closed” position, no fuel is provided and thus the heat is off.
In a two-stage furnace, there are actually two positions apart from “closed” that allow the furnace to heat your home in different ways, on high or low heat. Like a one-stage furnace, there is a “full-open position”, but what makes a two-stage unit unique is the second, “partially-open” position.
Using a different programming system than a typical one-stage furnace, a two-stage furnace system can better determine how your home needs to be heated: using full heat, much like a standard one-stage furnace, or the reduced heating power offered by the second, partially-open position on mild-temperature days. This partial position only provides 60% to 65% of the power that the full-open position does, based on how often your thermostat turns the furnace on and off and offers advantages to the fixed, open position of a one-stage furnace.

Advantages of Two-Stage Furnaces Over One-Stage

Like most machines or products that offer more than one setting, two-stage furnaces have many advantages that one-stage systems can’t meet. Depending on your personal heating needs, these benefits can help tip the scales when deciding on the system that is right for you.

  • More Energy Efficient
    Because a two-stage furnace spends most of its time running in the partially-open position, it ultimately uses less fuel than a one-stage system constantly running at full capacity that only shuts off when the desired temperature has been met.
  • Better Air Filtration
    As a two-stage furnace runs more continuously in the partially-open position, this allows more air to circulate and pass through the filter, increasing chances of pollutants and allergens being trapped. This creates cleaner air for you to breathe while indoors.
  • Quieter Operation
    Especially if your furnace is located near a living room or bedroom, you’ll notice that a two-stage system is much quieter than a one-stage furnace. This is the result of the furnace not needing to “kick” on and off so frequently or at 100% power.
  • Balanced Heating
    Two-stage furnaces allow for more consistent heating without the drastic temperature changes that can be experienced with a one-stage furnace. Instead of firing at full capacity each time it runs, a two-stage furnace can keep temperatures fluctuations within only a couple degrees of the thermostat.

Is a Two-Stage Furnace Worth the Money?

Though typically priced anywhere from $500 to $1000 higher than one-stage furnaces, two-stage furnaces can ultimately save you money in the long run due to their energy efficiency. It’s hard to put a price on comfort or justify the initial price tag, but if the benefits outweigh the negatives, a two-stage furnace is definitely worth investing in. Especially when considering your regional climate, a two-stage furnace may be the better choice to cut down on energy bills and eventually offset the higher price.
It’s clear that a two-stage furnace goes above and beyond the comfort and personalization offered by a one-stage unit. Depending on your budget and climate, a two-stage system can improve the quality of your indoor air and even save you money in ways that a one-stage furnace simply cannot. Of course, that comes at an expense, but if you’re dealing with a trusted professional who can help you consider your heating needs, it’s a worthy investment and one that can transform your everyday life in ways you may not even imagine.

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