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When Should You Replace An Old Gas Furnace? 5 Key Signs

When Should You Replace An Old Gas Furnace? 5 Key Signs

When should you replace a furnace? 

In one sense, this question has a fairly straightforward answer: If you’re paying too much to keep your building comfortable—and you’re exhausting your annual maintenance budget—you’re probably due for an upgrade. 

Of course, deciding whether to upgrade isn’t always easy. Heating systems are expensive investments, and the process of replacing an old furnace can be disruptive for residents. Unfortunately, waiting to address the problem can be much more expensive. Below, we’ll review some of the telltale indications of when a furnace should be replaced—and how upgrading to an eco-friendly heat pump can help you keep control of your budget.

Need to replace your old gas furnace? Try an energy-efficient heat pump. Answer a few quick questions to see if your building is eligible.

When should you replace a furnace? 

To determine when to replace a furnace, it’s helpful to understand the basics. Gas furnaces work by combusting natural gas to heat cold air via a heat exchanger. This process creates exhaust gases, including carbon monoxide, which is vented out of the building through a pipe. A blower fan diverts the hot air throughout the building. 

With this process in mind, you’ll need to look for telltale signs that your gas furnace isn’t operating as expected. If any component begins to fail, the system loses efficiency (and you’ll need to call in a service technician right away). Below are five indications that it could be time to replace your furnace.


1. Your furnace is approaching the end of its life expectancy.

Furnace life expectancy ranges from 15-30 years on average. Check your maintenance manual; if your system is approaching the end of that life expectancy, you’ll want to start planning on an upgrade. Some units can operate for much longer, but that doesn’t mean they’re worth hefty repair bills—older gas furnaces may be extremely inefficient.

The Federal Trade Commission requires central furnace and boiler manufacturers to measure annual fuel utilization efficiency (AFUE) for each unit. According to the Department of Energy, old gas furnace systems typically have an AFUE of 56% to 70%. In other words, an older system may waste between 30% to 44% of the fuel it consumes.

Upgrading to a new heating system can reduce your energy bills substantially, especially if the system utilizes eco-friendly technologies. Air source heat pump systems reduce energy usage for heating by about 50% on average.


2. Your furnace is making unusual noises.

Gas furnaces can be noisy, even when they’re operating as intended, but some noises indicate an impending failure. Some of those noises include:

  • Thumping—Imbalances in the blower motor can cause a thumping sound, which may occur consistently or when the unit powers on or off. 
  • Grinding—Grinding sounds can also indicate a blower motor issue. 
  • Pops, Bangs and Rumbling—These sounds can indicate that fuel continues to burn in the furnace’s combustion chamber, or the furnace’s burners may be unable to operate as intended.
  • Clicking—Consistent clicking sounds can indicate a problem with the furnace’s compressor.

Some sounds can be symptoms of potentially dangerous issues, so if you notice unusual noises while your furnace is operating, contact a service technician right away (and check out #5 on this list while you’re at it).  


3. Your building is experiencing poor air quality.

About 50% of all illnesses are caused or aggravated by poor indoor air quality, and combustion-based systems generate more harmful pollutants than eco-friendly alternatives. While most furnaces expel exhaust (or flue gases) outdoors, gases tend to make their way back into the building—combustion byproducts might reenter your building through open windows or travel in through gaps and cracks in venting. 

All gas furnaces exhaust flue gases, but older units can have an outsized effect on air quality. As your system ages, it will become less adept at managing humidity levels, and humid air can hold onto toxic contaminants. This can lead to an increase in tenant complaints, and you can’t always address the issue by cleaning ductwork or replacing filters. 

An older system may also generate excess carbon monoxide, which can be dangerous for residents. In addition to installing carbon monoxide detectors, check the pilot light regularly. If the pilot light flickers or turns yellow, it requires immediate attention.


4. Your furnace is operating more frequently.

Gas furnaces generate intense heat, but over time they become less capable of delivering that heat. As efficiency drops, the furnace’s thermostat will trigger operation more often. 

This has a cyclical effect—the more frequently the furnace operates, the more stress the system puts on its blower motor and other mechanical components. Even if your system operates near-constantly, you may notice other signs of efficiency loss. In larger buildings, tenants on higher floors may not get enough heat. 


5. Your furnace maintenance costs are growing.

Maintenance expenses can be a powerful indicator: If you’ve got your furnace technician on speed dial, your system may be due for replacement. 

As gas furnaces age, they require more attention. Some issues like malfunctioning thermostats may be easy to address, but a major mechanical problem such as a cracked heat exchanger will quickly increase your annual cost of ownership. 

If you’re still not sure when to replace a gas furnace, ask your service provider. A reputable technician can inform you when your system is ready for replacement. Take their advice; heating systems tend to break down when they’re heavily used. If your system is showing signs of wear, it’s more likely to fail during cold weather, when repair technicians and installers are in high demand. 

When replacing a gas furnace, consider an energy-efficient upgrade.

Retrofitting an old furnace isn’t always an option, particularly if a furnace is already showing signs of impaired operation. You’ll want to replace your furnace if it’s near the end of its expected lifespan. 


Do I need to replace my gas furnace with another furnace?

In most cases, no. Modern heating technology can help you limit the costs of replacements. Air source heat pumps are an energy-efficient, ecologically sound alternative to combustion heating. Unlike traditional systems, an air source heat pump uses ambient air to provide both heating and cooling, and they’re a great way to add value to your property while improving comfort.

The good news: Heat pumps are a cost-effective option for most buildings. Ducted heat pumps can deliver air through your building’s existing ductwork; while ducted systems are less efficient than mini-split systems (which deliver air directly through an indoor unit), they still offer improved energy consumption over gas-powered heating systems. 

Some of the benefits of a heat pump system include:

  • Heat pumps are excellent air purifiers, and some systems can be outfitted with HEPA filters to further improve air quality. They’re effective at managing humidity in both hot and cold climates. 
  • Heat pumps require less regular maintenance than traditional heating systems. Since heat pumps also provide cooling, you’ll schedule a single maintenance visit (instead of separate appointments for your furnace and air conditioning systems). 
  • Mini-split heat pump systems deliver air through individual indoor units. Tenants have more control over room temperatures. 

For a more detailed analysis of heat pumps work, read our resource: “What Is An Air Source Heat Pump (ASHP)? Your Go-To Guide.”

Replace your gas furnace with state-of-the-art heating and cooling technology.

An older gas furnace can become an expensive liability. Heat pump systems can carry larger upfront costs, but they offer a better return on investment than fuel-combustion heating in the long term. There are more ways to reduce your out-of-pocket expenses: Many state and local governments offer rebate programs for heating and cooling systems that meet certain specifications.

BlocPower specializes in providing energy-efficient heating and cooling systems. Our team is dedicated to helping you find the best option for your building, and we work with our clients to find financing options that make sense—including energy service agreements with low, predictable payments. 

By upgrading, you’ll enjoy cleaner air, improved comfort, and lower energy bills. Take the first steps today and find out if BlocPower is available in your area.