7 Ways to Tell If You Need to Replace Your Furnace

Your furnace has served you well for however long you have had it. Sure, you might have had some ups and downs, and there might have been times when the furnace needed repair or some attention. For the most part, though, it has been able to do the job of keeping your home comfortable for years.

There comes a point, however, when even the most reliable of furnaces need to be replaced. Often, a furnace will provide some hints and signs that it is due for replacement. Here is what to keep an eye out for when deciding whether your best option is to repair or replace your furnace.

1. You Are Dealing With Frequent Furnace Repairs

It is a chilly day, so you turn the thermostat up a few degrees. Your furnace starts to cycle on, then nothing happens. Or, maybe you have noticed that your gas furnace is not working at all.

That might not seem like a big deal if it happens once during a season or once over the course of several years. But when your furnace starts to malfunction frequently or when you are calling in a repair technician every year to do more than a simple inspection and tune-up, it might make more sense economically to replace the furnace.

At a quick glance, it costs less to repair a furnace than to invest in an entirely new one. Repair bills can usually be in the few hundred dollar range, while replacement bills can be in the several thousand dollar range. Once you have two or more repair bills, though, or if you are paying to fix up the furnace every single year, you are likely to find that you end up spending more on your old furnace than you would on a new model.

To determine whether a replacement furnace is worth it financially, look at the price of your repair bills. If you have a newer furnace and your bills are half of the cost of getting a new furnace or more, it makes sense to replace it. The point at which it makes financial sense to replace an older furnace is even lower. If your furnace is over 10 or 15 years old, you will want to consider replacing it if the repair bill is around 10 or 20% of the price.

Replacing a furnace that constantly needs repairs will do more than help you save money. It also saves you time. Rather than having to call in a technician multiple times a year, you can have the replacement installation performed once, leaving you free to live your life and take care of your family and household.

2. Your Heating Bills Have Been Rising Drastically

Furnaces work by burning fuel, such as heating oil or propane gas, to produce heat. In a perfect world, 100% of the energy used by the furnace should go into producing heat. In reality, the percentage is less than 100%, even among the most energy-efficient oil or gas furnaces.

Generally speaking, the older your furnace is, the less energy-efficient it is likely to be. The reduced energy efficiency is due to two factors. One, the design of older models is usually not as efficient as the design of newer furnaces. Two, furnaces become less energy-efficient as they age, due to wear and tear on their parts and system.

The annual fuel utilization efficiency, or AFUE, measures the energy efficiency of a furnace. AFUE compares the total heat produced by the furnace to the amount of fuel energy it uses. The higher the AFUE rating, the more efficient a furnace will be. The minimum AFUE rating of a residential furnace is 78. Furnaces that earn the Energy Star label need an AFUE rating of at least 85 for oil-powered systems or 90 for gas-powered systems in the U.S. South.

One of the signs that your furnace is losing energy efficiency is an increase in your home’s energy bills. If you are heating your home to the same temperature as in past years and the weather has not been unusually cold, but you need to refill your oil or propane tank more frequently, it is a good idea to check on your furnace. The problem could be a small and easily fixable one, such as replacing the filters to help the furnace run more smoothly. However, it could be that the furnace needs a more complex repair to restore it to its previous efficiency.

If the furnace is older, you are likely better off replacing it with a newer, more energy-efficient model. You will save money in the long run on repair bills and energy bills.

3. Your Furnace Is Old

Older furnaces use more energy than newer models. They are also more prone to breakdowns and more likely to need costly repairs.

How can you tell if your furnace is too old and should be replaced? The advertised gas or oil furnace life expectancy is often 20 to 30 years. Usually, though, once a furnace hits the 10- or 15-year mark, it is time to start considering replacement. Your furnace might reach its 20th or even 30th birthday, but it might also cost you a lot in terms of repair bills or higher energy use in that time.

If you find yourself calling a technician frequently or if your energy bills are higher than they were in the past, your older furnace might be due for replacement. If you are not sure if your older furnace should be replaced, SMO Energy is here to help. During an in-home energy consultation, we will take a look at your current system, measure your home and discuss your energy needs with you to determine if a new furnace is the right choice.

4. Your Furnace Has Been Making Noises

Every furnace makes some noise when it operates. It is likely to hum as the burner turns on and ignites the fuel. You are likely to hear a whooshing sound as the air travels through the ducts in your home. Once a cycle is over, you might hear popping or pinging noises as the ducts cool off.

Some furnace noises can be a cause for concern. For example, a single loud boom coming from the furnace can be a sign that fuel has built up in the system and has ignited all at once when the furnace switched on. Fuel buildup can occur if the burners are dirty or if there is an issue with the valve. In some cases, the buildup can cause the heat exchanger to crack, which might require an expensive repair or total replacement of the system. 

Other furnace noises that can signal it is time for a replacement include:

  • Shrieking: A high-pitched shriek or the sound of metal scraping against metal can mean something has fallen out of place, broken off or otherwise come loose. Depending on the extent of the damage, a new furnace might be your best option.
  • Whining: A high-pitched whine can point to a problem throughout the furnace. A trained technician will be able to examine your furnace and detect the source of the whining noise, as well as recommend what to do next.
  • Rumbling: A furnace might rumble as the air travels through the ducts or right as the fuel ignites. But if the rumble is persistent and loud, it could be a sign that there is an issue with the burner or ignition system.

5. Your Furnace Is Starting to Look Different

When it was first installed, your home’s furnace most likely looked shiny and new. As the years have gone by, it has likely lost that shiny newness. While it is common for appliances to start to show signs of wear and tear, at some point, those signs can signal that is it time to replace your equipment. Some appearance changes to keep an eye out for include:

  • Rust: A furnace can rust in areas where metal is exposed to combustion gases. Over time, rust can be an issue as it weakens the structure of the furnace. Cracks can develop in rusted areas, increasing the chance of leaks and other issues. If your furnace has become very rusty over time, the best thing to do might be to have a new one installed.
  • Streaks of soot: Soot forms as a result of incomplete combustion and that incomplete combustion can mean that the furnace is producing high amounts of carbon monoxide. Cleaning the furnace and having it inspected can help. Your technician might recommend replacement based on the age and overall condition of the system.
  • Cracks: Cracks can form in a furnace as a result of extensive rusting or due to issues with the heat exchanger. Any type or size of crack should be a cause for concern, so if you see one, call a technician to have them assess the situation and let you know what to do next.

6. You Are Experiencing Humidity Issues


It is not just temperature that affects your home’s comfort level. It is also the amount of moisture, or humidity, in the air. When the air in a home is very humid, mold can thrive, which can contribute to breathing problems and respiratory illnesses. High humidity levels can also cause the walls and structures of a house to rot and can lead to the formation of stains on the walls and ceilings. Some pests love moisture and are more likely to infest humid homes.

Humidity levels that are too low can also be a cause for concern. Dry air can dry out the skin, making it flaky and itchy. Dry air also dries out the nasal passages, potentially causing respiratory issues or trouble breathing. When the humidity in a home is too low, you are more likely to get shocks from static electricity, too. 

Newer furnaces are often better equipped to deal with humidity concerns compared to older models. If your home is very dry in the colder months of the year, your furnace might be playing a significant role in the overall air quality. Upgrading to a new model, perhaps a new model with a humidifier built-in, might help to solve your problem.

7. Your House Feels Unevenly Heated

Ideally, your furnace should heat all areas of your home evenly. As it gets older, though, it might have difficulty pushing the same amount of warm air to all parts of the house. That can be particularly true if you have a multi-story home or if some rooms are farther away from the furnace than others.

Age is not the only reason why a furnace might struggle to heat your home evenly. If the system is too large or too small for the size of your home,  it can have trouble providing even heat. An over-sized furnace might cycle on and off frequently and might never have the opportunity to deliver heat to distant rooms. A furnace that is undersized might work too hard, overheating some areas while others stay cold.

Uneven heat in the home is not always caused by the condition or size of the furnace, which is why it is a good idea to have one of SMO Energy’s certified and trained technicians evaluate your situation. It could be that your furnace simply needs new air filters or that one of the vents in one of the rooms is closed off or otherwise blocked. After assessing the situation, our technicians can help decide if repair or replacement is the way to go.

Schedule an Energy Consultation With SMO Energy Today

Are you wondering when to replace a gas furnace or oil furnace? SMO Energy can help you decide. We have been serving residents of Southern Maryland since 1926 and are happy to listen to your concerns, evaluate the condition of your furnace and help you decide what to do next. Contact us today to set up a free, in-home energy consultation and to learn more about furnace replacement and our other services.

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