Quick checklist: signs you need a new furnace
Age
15 years or older (check the date on the rating plate inside the furnace door).
Efficiency
A metal flue into the chimney usually means an older 80% AFUE or lower furnace.
Repairs
Two or more significant repairs in the last two winters.
Bills
Gas use climbing year over year with similar weather and habits.
Comfort
Cold rooms, long run times, or a house that cannot keep up below −20 °C.
Safety
Yellow or wavering flame, soot, rust on the heat exchanger, CO alarms, or a red tag.
Noise
New banging, screeching or rumbling that returns after repairs.
Air quality
More dust, dry air or odours than you used to notice.
One sign on its own usually means a repair. Three or more, especially with age, means it is time to plan a replacement.
1. Your furnace is 15 years or older
A well-maintained gas furnace typically lasts 15–20 years in Ottawa. Our long heating season, often from October to April, puts more hours on a furnace than in milder climates. Once yours passes 15, every repair is a bet on a machine near the end of its design life.
Find the age on the rating plate inside the furnace door, often in the serial number, or on old installation paperwork. If you bought the house with the furnace, the home inspection report may list it. Our furnace lifespan guide explains what shortens and extends a furnace’s life.
2. It is an older, lower-efficiency model
Furnace efficiency is measured in AFUE, the share of fuel that becomes heat in your home. Every new gas furnace in Canada must be at least 95% AFUE.
| Furnace type | Typical AFUE | How to spot it | Gas lost per $100 |
|---|---|---|---|
| Old standing pilot (pre-1990s) | About 55–65% | Pilot flame always on, metal flue | $35–$45 |
| Mid-efficiency | About 78–82% | Metal flue into chimney, inducer fan | About $20 |
| High-efficiency (older) | 90–95% | White PVC pipes out the wall | $5–$10 |
| New high-efficiency | 96–99% | PVC pipes, often two-stage or modulating | $1–$4 |
If you still have a mid-efficiency furnace, a new 96–98% model cuts the gas lost up the chimney by roughly three-quarters. Learn how ratings work in our AFUE, SEER2 and HSPF2 guide.
3. Gas bills keep rising
Compare your Enbridge Gas bills for the same months in past years, looking at cubic metres (m³) used rather than dollars, since rates change. If usage keeps climbing while the weather and your habits have not changed, the furnace is likely losing efficiency to worn parts, dirty burners or a failing blower.
A tune-up can recover some lost efficiency on a younger furnace. On a furnace over 15 years old, rising usage is usually a sign of age that maintenance cannot fully reverse.
4. Repairs are becoming a habit
Most furnace repairs in Ottawa cost $150 – $900, while major parts such as a blower motor, control board or inducer typically run $600 – $2,000. One repair on a 10-year-old furnace is normal. Two or three major repairs in a couple of winters on a 15-year-old furnace is a pattern.
A handy rule: multiply the furnace’s age by the repair cost. If the result is over $5,000, replacement is usually the smarter move. Our repair or replace decision guide walks through real examples.
5. Rooms stay cold or the furnace runs non-stop
If upstairs bedrooms are cold, the basement is chilly, or the furnace runs constantly on −25 °C nights and still falls behind, the furnace may be worn, undersized, or simply a single-stage unit that heats unevenly.
Not every cold room means a new furnace. Blocked returns, leaky ducts, closed dampers and poor attic insulation cause similar symptoms. A good technician checks airflow and duct pressure before recommending replacement. If you do replace, a properly sized two-stage or modulating furnace with a variable-speed blower is the best fix for uneven heating; see our furnace brands and types guide.
6. Safety warning signs
Some signs override everything else. Treat these seriously:
Yellow, orange or wavering flame
Instead of a steady blue one, which can signal poor combustion.
Soot or scorch marks
Around the burner area or furnace door.
A carbon monoxide alarm
Going off, or headaches, nausea or drowsiness that ease when you leave home.
Rust, cracks or holes
Found on the heat exchanger during a tune-up.
A red tag
From a licensed technician, which means the furnace must not run until the hazard is fixed under TSSA rules.
A cracked heat exchanger on an older furnace almost always means replacement. Make sure you have working CO alarms near every sleeping area. Read more in our furnace carbon monoxide safety guide.
7. New noises, dust and dry air
Banging at ignition, screeching from the blower or rumbling after the burners shut off can point to worn motors, delayed ignition or a failing inducer. Persistent new noises on an older furnace often mean several parts are wearing out together.
More dust on furniture, stale odours or very dry air can also point to an aging system, leaky return ducts or a humidifier that no longer works. A new furnace is a good time to add a media filter, a humidifier or an HRV.
Why replace before winter, not during it
Replacing a furnace in September or October is calmer and gives you more choice. In a January cold snap, you are choosing from whatever is in stock, with the house getting colder by the hour.
Better selection
Of models, brands and furnace types.
Time to compare
Quotes, check rebates and arrange financing.
No emergency stress
Or space heaters while you wait.
A fresh system
That has been tested before the first −25 °C night.
A high-efficiency gas furnace replacement typically costs $4,500 – $8,500 installed in Ottawa, with variable-speed or modulating models up to about $10,500. The final price depends on the home, the equipment and the venting and ductwork. Oria gives free quotes on any equipment purchase, and financing starts from $49/month on approved credit. See our furnace replacement cost guide for details.
How to make your current furnace last
If your furnace is still in good shape, a few habits help it reach the upper end of its lifespan: change the filter every 1–3 months, book a tune-up every fall, keep the outdoor intake and exhaust pipes clear of snow, and fix small problems before they become big ones.
Ready to plan? Oria has installed furnaces across Ottawa since 2014 and is a Lennox authorized dealer that also installs Goodman and other major brands. Alex G. said it well: “Clean professional and reliable.” Book a free quote through our furnace installation page or call (613) 866-1869.
Frequently Asked Questions
How do I know if my furnace needs to be replaced?
Replace your furnace if it is 15 years or older and needs a major repair, if repairs are becoming frequent, if gas use keeps rising, or if rooms will not stay warm. Safety findings, such as a cracked heat exchanger, a yellow flame, soot or carbon monoxide alarms, are reasons to replace no matter the age.
How long does a furnace last in Ottawa?
A well-maintained gas furnace typically lasts 15–20 years in Ottawa. The long heating season, from about October to April, puts many hours on the equipment. Furnaces that were oversized, poorly installed or rarely serviced often fail sooner. Yearly tune-ups and regular filter changes help a furnace reach the upper end of that range.
Is it better to replace a furnace in fall or winter?
Fall is better. In September and October you have more choice of models, time to compare quotes and check rebates, and no emergency pressure. In mid-winter, a failed furnace means a cold house, possible frozen pipes and a rushed decision. If your furnace is showing several warning signs, plan the replacement before the first deep freeze.
What does a yellow flame on a furnace mean?
A healthy gas furnace burns with a steady blue flame. A yellow, orange or wavering flame can mean incomplete combustion from dirty burners, poor air supply or a venting issue, which can produce carbon monoxide. Turn the furnace off if you also see soot or have CO alarms sounding, and have a licensed gas technician inspect it right away.
How much does a new furnace cost in Ottawa?
A high-efficiency gas furnace replacement (96–98% AFUE) typically costs $4,500 – $8,500 installed in Ottawa, and variable-speed or modulating models can reach about $10,500. The final price depends on the home, the equipment and the venting and ductwork. Oria gives free quotes on any equipment purchase, and financing is available from $49/month on approved credit.
Can I just repair my old furnace instead?
Often, yes, if it is under about 12–15 years old, the repair is modest and there are no safety issues. Multiply the furnace’s age by the repair cost. If the result is under $5,000, repair usually makes sense. Over $5,000, or with a cracked heat exchanger, replacement is usually the better investment for an Ottawa home.
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