If your furnace is 20 years old, replacement is usually the smartest and safest move. Some furnaces can run past age 20. However, these furnaces are typically expensive to run and prone to inconvenient breakdowns. By upgrading to a modern furnace, you can improve your comfort, reduce your energy bills, and worry less about equipment failures.
Still not sure if you should replace your 20-year-old furnace? In this blog, we’ll walk through the signs your furnace is failing, how much longer it might last, and what benefits come with replacing it now. If you’re on the fence, this guide will help you make the right call.
What Kind of Furnace Do You Have?
Most furnaces in homes today run on natural gas, but others use electricity, propane, or oil. Your furnace’s fuel type can affect its efficiency, maintenance needs, operating costs, and expected lifespan:
- Gas furnaces are common and typically last 15–20 years with routine maintenance.
- Electric furnaces can last even longer (20–30 years). However, they may cost more to operate depending on electricity rates.
- Propane and oil furnaces are still used in rural areas but often require more upkeep and tend to wear out faster.
Regardless of the fuel type, a 20-year-old furnace is likely past its prime in terms of performance, energy efficiency, and safety. For the most part, 20-year-old furnaces are ready to be replaced.
Don’t Wait for a Breakdown
It’s tempting to squeeze another season out of your old furnace, but doing so can backfire. If your furnace fails in the middle of a cold snap, you’re left scrambling for emergency service (and making rushed decisions under pressure).
By replacing your furnace before it dies, you get to:
- Research your options
- Compare models
- Take advantage of off-season deals
- Avoid the stress of a no-heat emergency
Planned replacement is almost always cheaper and safer than reactive replacement.
Signs It’s Time to Replace Your Furnace
If your furnace checks off one or more of the issues below, it’s a strong sign that replacement is overdue:
- Frequent repairs
- Higher energy bills
- Inconsistent heating
- Strange noises or smells
- Yellow pilot light
- Poor air quality
- Rust or corrosion
- Cracked heat exchanger
These symptoms don’t just mean your system is aging. They point to declining performance, rising risks, and growing costs. In many cases, they signal that your furnace is nearing the end of its usable life and could fail when you need it most.
Carbon Monoxide: The Hidden Danger of Old Furnaces
One of the most serious risks with aging furnaces is a cracked heat exchanger. This internal component can develop small fractures over time, especially in older gas models. When that happens, carbon monoxide can leak into your home undetected. Carbon monoxide is a deadly, odorless gas.
Signs of a potential carbon monoxide issue include:
- Flu-like symptoms (headaches, dizziness, nausea)
- Soot around furnace vents
- A yellow, flickering pilot light instead of a steady blue flame
You must have your furnace inspected if it’s over 20 years old to check for this issue.
What About Air Quality?
Aside from wasting energy, old furnaces can also negatively affect your indoor air quality. Aging systems:
- Circulate more dust and allergens
- Struggle to regulate humidity, leading to dry air or mold-friendly conditions
- May fail to properly vent harmful combustion gases
If you’ve noticed more sneezing, dry skin, or general stuffiness, your furnace could be part of the problem. A new system with upgraded filtration can make a big difference.
Repair or Replace? Here’s How to Decide
Sometimes, a minor repair is all you need. But when your furnace is 20 years old, even small fixes can become frequent and costly. Here’s a breakdown to help guide your decision:
- Choose repair if the issue is minor (under $500), the part is readily available, and your furnace is still under 15 years old with a generally good track record.
- Choose replacement if your furnace is over 20 years old, your energy bills are climbing, or you’re calling for service more than once a year. Replacement also makes sense if you’re looking for better air quality, quieter performance, or improved control with smart thermostat compatibility.
As a general rule, if …
- The repair cost is more than 25% of the cost of a new system, and
- Your furnace is already past 15 years
… it’s likely time to replace it.
You’ll save more in the long run by upgrading to a more efficient, reliable system.
Not Sure What to Do Next? We’ll Help You Decide
Whether your furnace needs a small fix or a full replacement, you don’t have to figure it out alone. Our experienced techs will inspect your system, explain your options clearly, and guide you toward the best solution for your home.
Learn more about furnace installation at 5 Star HVAC Contractors.
