How long does a furnace last? Know when you should replace

The cost of a new furnace is a considered investment for your home. But when you consider how long a furnace lasts, the upfront cost isn’t so unnerving.

Let’s explore the life expectancy of a furnace and how you can make yours last longer. Plus, we’ll offer symptoms of a failing furnace and cues on when to repair vs. replace the unit.

Average furnace lifespan

A quality furnace can last 10 to 40 years. The unit’s lifespan depends, in part, on its fuel source, how often it’s used, and the cadence of routine maintenance.

Here’s a closer look at the average life expectancies of gas, electric, and oil furnaces. Note that these numbers only apply if your unit is regularly maintained.

If you’re taking proper care of your furnace, it should last longer than 10 years. Plus, most units come with 10-year parts warranty.

How long does a gas furnace last?

A gas furnace can last between 15 and 20 years. Gas furnaces usually don’t last as long as oil or electric furnaces, but they’ll warm your space the fastest.

How long does an electric furnace last?

An electric furnace can last from 20 to 30 years. While electric furnaces are more expensive to operate than gas, you may get an extra decade of heat.

How long does an oil furnace last?

An oil furnace can last 30 or more years. This fuel source is less common today, but the cast iron heat exchangers help them outlast other models.

How long does a furnace filter last?

How long a furnace filter lasts depends on lifestyle characteristics, like pets or smoking in the home. The filter’s thickness may also indicate how often it should be replaced. The table below shows our suggested timeframe for changing your furnace filter.

Check the cleanliness of your filter once a month. Regularly replace your filter during the cold season to ensure the best energy efficiency from your furnace. Check your filter’s label for the manufacturer recommendation.

Filter Thickness (inches)	Replacement time (months)
1-2”	1-3
3-4”	6-9
5-6”	9-12

What impacts how long my furnace lasts?

While fuel source is a major point to consider, it’s not the only factor at play. A range of issues can extend or shorten your furnace’s lifespan.

• Maintenance: Regular upkeep is the key to a long-lasting furnace. While yearly inspection is a must, we’d recommend getting yours checked out twice a year.
• Unit quality: When it comes to furnace lifespan, you often get what you pay for. Premium units usually outlast value and mid-range models.
• Extreme thermostat setting: If your furnace is regularly set too high or low, your unit will overexert itself. When the furnace is constantly overworking to keep up, it’s more likely to break down. A reading above 60 and below 80 is ideal.
• Ductwork: If your vents are improperly sealed, your furnace will overwork to compensate for the lost air. The unit also becomes a breeding ground for dust and debris buildup, which results in a shorter lifespan.
• Sizing: A furnace that’s too small for your space will quickly burn out, draining its lifespan. Check that your furnace has the right energy output for your space.
• Placement: If your furnace is in a moisture-dense area of your home, the heat exchanger may corrode over time.

Is it time to replace my furnace?

Most furnaces come with a limited 10-year warranty. Once that time runs out, though, you’re on the hook for parts, labor, and more.

If it isn’t broken, don’t fix it (but do schedule your yearly routine inspection). A furnace that’s 15+ years old but has no issues isn’t worth replacing in our book.

Still, a combination of the factors below could be telltale signs your furnace may be nearing its end. Before you spend hundreds on a shiny new unit, call an HVAC professional to confirm.

• Age: If your furnace is 20+ years old, you may want to consider a new unit. Newer models offer better energy usage, cool features like smart thermostats, and more.
• Noise level: As furnace components age and weaken, they have to work harder to bring the same amount of heat. This means you’ll hear a louder baseline operation. Popping and humming noises are also more common as your furnace ages.
• Temperature shifts: Did your room go from the Sahara to the Arctic in a flash? It’s not you, it’s your furnace. As furnaces age, they can’t maintain a steady temperature as effectively.
• Energy bills spike: Furnaces get less energy efficient as they age. If you’re noticing sky-high energy bills out of nowhere, your furnace may be tapping out.

5 ways to extend the lifespan of your furnace

For better or for worse, your furnace life expectancy is what you make it. Every model is different, but a few steps of preventative care can add years to your furnace’s lifespan.

1. Maintenance: We can’t overstate the importance of regular furnace check-ups. Inspections extend the functional years of your furnace by resolving small issues before they snowball. Minimally, we recommend annual inspections, but twice a year is best. 
2. Change your filters: It’s a point worth repeating. Clean filters keep dust and debris away. Ideally, you should replace a filter of any size every three months. For a more realistic timeline, check our “How long does a filter last?” section above. 
3. Keep it low: Auto mode is your best friend with furnace fans. If your fan is constantly running on high, your unit will burn out overtime. Keep your fan running low when you comfortably can, and your furnace will thank you. 
4. Keep it mild: You should keep your thermostat set between 60 and 80 degrees Fahrenheit. If your furnace is having to meet an extreme demand, it won’t run at its best. 
5. Smart thermostat: Smart thermostats can clue you into your power usage and use energy-saving modes. With these tools on hand, you can customize your heating and keep your furnace running longer. 

Consider a furnace replacement if your unit is 15+ years old and continuously needs repairs. Extend the life of a good furnace by keeping it clean and scheduling regular maintenance.

A quality furnace can warm your home for generations. Use the furnace cost calculator to determine a price range for replacing your unit.