Updated On

November 9, 2023

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    Figuring out when to replace a furnace is not as straightforward as it initially seems. Without experience working on HVAC systems, how are you supposed to tell whether or not those strange noises emanating from your furnace are a problem?

    We put together this handy guide to help you troubleshoot your furnace problems and decide if you need to replace your furnace — or if you can get by with a simple repair. If it turns out that you need to replace your furnace, we encourage you to get several quotes from the best HVAC companies in your area before making your decision.

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    • An older furnace or one that’s not working as well as it used to might need to be replaced.
    • Furnaces typically last between 15 and 25 years.
    • Repairing a furnace can get expensive, so it’s often more cost-effective to replace it.

    What are the Signs It’s Time To Replace Your Furnace?

    Diagnosing your furnace’s health before it fails is essential for avoiding the headaches and expenses of needing an emergency furnace replacement. If you’re unsure whether or not your furnace is on its last legs, Here are the five most common ways to determine the ideal time for furnace replacement:

    It’s Getting Old

    Even if your old furnace isn’t showing negative signs, you’re better off not waiting until it fails to consider getting a new one. We know this sounds like generic advice, but keeping your furnace’s age in mind can help you detect that it’s failing faster than you otherwise might.

    If your furnace is more than 15 years old, small warning signs carry more weight — including more frequent or longer runs to reach your desired temperature. Most furnaces don’t fail suddenly without warning, so it’s possible to predict their failure if you’re paying attention.

    More Frequent Repairs

    A string of furnace repairs is annoying and expensive, but it might be more than just bad luck. As furnaces age, their components wear out — leading to repeat visits from your neighborhood HVAC contractor.

    Furnaces last between 15 and 25 years on average, but individual components may start to fail earlier. Here are some common furnace repairs you might encounter as your furnace ages:

    • Blower Motor: If your blower motor isn’t working properly, your furnace won’t have the airflow needed to heat and circulate air throughout your home. Even worse, a struggling blower motor strains other parts of your furnace — which can lead to a cascade of issues.
    • Cracked Heat Exchanger: This is an emergency that requires immediate repair. A cracked heat exchanger could release carbon monoxide into your home, so you should call a professional HVAC tech immediately if you suspect your heat exchanger is compromised. Unfortunately, replacing the entire furnace is often more cost-effective since repairing the heat exchanger is very expensive — when even possible.
    • Ignition: It’s common for a furnace’s ignition system to experience issues as the furnace ages. Cycling on and off more frequently than normal or not turning on at all is a telltale sign that your furnace’s ignition system is faulty.
    • Thermostat: Your thermostat is the brain of your entire HVAC system. A bad thermostat can cause your furnace to turn on more or less frequently, so it can be hard to tell when it needs to be replaced.

    Furnaces will encounter problems that require repairs throughout their lives, but several issues in a short period could indicate a more systemic problem.

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    If you need to replace the blower motor, the thermostat, and the ignition system, you should start seriously thinking about biting the bullet and replacing the furnace.

    Noticeable Increase in Your Energy Bill

    One of the earliest signs that your furnace could be starting to go is a steady increase in energy costs over a few months. As furnaces age, their energy efficiency decreases, meaning they need to work harder to keep your home at a comfortable temperature. This efficiency reduction is mostly due to ordinary wear and tear but could be exacerbated by neglecting regular maintenance.

    Before you run out to replace your furnace, it’s worth checking a few things first:

    • Check for leaks: Leaks can make your furnace work harder than normal. Have a licensed furnace maintenance technician inspect your furnace for leaks before you decide it’s time for a replacement.
    • Ensure proper furnace ventilation: Furnaces need good ventilation to operate efficiently. If your furnace is situated where its vents may be unintentionally obstructed, such as a basement or attic, inspect the area to confirm that no items have been inadvertently placed in front of the vents.
    • Replace the filter: Furnace filters must be replaced every three to four months. If your filter is old and full of dust or debris, it could cause an airflow blockage, which requires your furnace to expend more energy to keep the air circulating. Replacing the filter helps with energy efficiency and improves indoor air quality in your home.

    Aging windows and doors can also lead to increased utility bills due to leakage, so be sure to check those, too.

    Uneven Heating

    Another sign that your furnace might be on its way out is that it no longer heats your home evenly. Uneven heating is often a symptom of duct issues like leaks or blockages. Your HVAC tech should be able to narrow down where there’s likely a problem based on what rooms aren’t receiving enough heat. Issues with the main duct are usually harder to locate since they affect the entire system, but a quick inspection is usually enough to tell there’s a problem. If the ductwork checks out, it could be an issue with the filter or blower motor.

    Unusual Noise

    Unusual clunking, rattling, or popping sounds could indicate that your furnace is not long for this world — or it could be a minor issue that’s easily fixable, like a loose screw or panel. Let’s go through a few different types of sounds and discuss their most likely causes:

    • Popping/Banging: These sounds are difficult to assess and could stem from several issues. Benign causes of popping include expanding and contracting ductwork and clogged vents. Banging sounds could also be caused by more serious problems, like a cracked heat exchanger or malfunctioning blower motor.
    • Rattling: Rattling is often a sign of a loose screw, panel, or some other physical part of your furnace. If you can locate the loose piece, resecuring it will often resolve the problem and eliminate the sound.
    • Squealing: A more serious sound is squealing, which is almost always caused by a worn fan belt. You should turn your furnace off and call a technician if you hear squealing to avoid damage to your furnace’s blower motor.

    If you can’t locate the issue after a quick inspection, contact an HVAC professional. Any changes in your furnace’s behavior could indicate that it’s approaching its end of life — especially the sudden onset of unusual noises. More serious problems don’t necessarily mean you’ll need to replace your entire furnace, but you should consult an experienced technician to find out.

    When Should You Replace Your Furnace by Type?

    The symptoms of an aging furnace are largely the same between different fuel types, and you can use the information from the previous section to decide whether or not it’s time to purchase a new one.

    Not all furnaces are created equally; some have longer average lifespans than others. Electric and natural gas furnaces typically last between 15 and 20 years, while oil furnaces can last up to 25 years if well-maintained. The tradeoff is that oil furnaces often cost more.

    The following table summarizes the different types of furnaces to help you decide which is right for your home.

    TypeLife spanAverage CostUnique Benefit
    Electric Furnace15–20 years$1,800 – $7,100Energy-efficient and more environmentally friendly
    Gas Furnace15–20 years$3,285 – $7,550Lower fuel costs and more effective heating
    Oil Furnace15–25 years$6,425 – $9,175Higher BTU output

    Should You Repair or Replace Your Furnace?

    If you or your HVAC technician think that an issue is isolated to a single component, you might be able to get away with repairing or replacing just that component instead of the entire system. Of course, you don’t want to wind up in a situation where you replace a new piece of the system every three months until you eventually need a new heating system.

    Another consideration is the repair costs. Springing for a $1,000 to $1,500 repair doesn’t make sense when a brand-new furnace may cost only slightly more.

    If you decide to replace your furnace rather than try to repair it, the best HVAC companies will use your home’s size, window placement, and interior room layout to help you choose the right system for your home and energy needs — including air conditioning options if needed. They may even recommend purchasing a heat pump or another combined heating and cooling system to save money on replacement costs.

    Check out the video below to see how the process might go.

    Planning to replace the furnace? Check out our guide to the top furnace brands to choose from.

    What’s Our Recommendation for When To Replace a Furnace?

    We’ve thrown a lot of information at you in this article, so let’s take a step back and simplify things. If your furnace can no longer heat your home effectively, it’s time for a new one. That could mean uneven heating, inefficient heating that leads to high monthly heating bills, or inability to produce enough heat.

    Most furnaces end their useful life after 15 to 20 years. If your current furnace is around or above that age and you start noticing it showing one or more of the above signs, you should contact your local HVAC companies and start surveying your options.

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    FAQs About Replacing a Furnace

    Can I replace my own furnace, or should I hire a professional?

    You can replace your own furnace if you have the necessary skills and tools, but we recommend hiring a professional. Professionals have the expertise and certifications to guarantee smooth installation and operation in adherence to safety codes. Incorrect installation may void warranties and pose risks to your home and family, so it’s usually not worth the money you’ll save by doing it yourself.

    Are there any tax credits or rebates available for furnace replacements?

    There may be tax credits or rebates available to help reduce the cost of a furnace replacement — depending on your location and the efficiency of the new furnace. Purchasing a high-efficiency furnace makes it more likely that your new furnace will be eligible for any incentive programs; Energy Star-certified products often qualify for these incentives.

    What is the best time of year to replace a furnace?

    The best time of year to replace a furnace is during the spring or fall. These seasons are typically less busy for HVAC professionals, allowing for easier scheduling, a greater chance of getting discounts, and a more comfortable home if the installation takes longer than you expect.

    How often should I have my furnace inspected?

    Your furnace should be inspected at least once a year, preferably before the heating season begins. Your HVAC installation company may even set you up with a routine annual appointment when you have it installed. Regular tune-ups ensure optimal performance, energy efficiency, and a longer life expectancy for your furnace. They also help identify potential breakdowns early, preventing costly repairs or replacements.

    Editorial Contributors
    avatar for Dan Simms

    Dan Simms


    Dan Simms worked in real estate management for five years before using his experience to help property owners maintain their own homes. He got his master’s degree in English Literature and Creative Writing, and he now enjoys sharing his knowledge about homeownership and DIY projects with others on Today’s Homeowner. When he’s not writing, he’s usually outdoors with his wife and his dog, enjoying mountain biking, skiing, and hiking.

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    photo of Roxanne Downer

    Roxanne Downer


    Roxanne Downer is a commerce editor at Today’s Homeowner, where she tackles everything from foundation repair to solar panel installation. She brings more than 15 years of writing and editing experience to bear in her meticulous approach to ensuring accurate, up-to-date, and engaging content. She’s previously edited for outlets including MSN, Architectural Digest, and Better Homes & Gardens. An alumna of the University of Pennsylvania, Roxanne is now an Oklahoma homeowner, DIY enthusiast, and the proud parent of a playful pug.

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