Two homes on the same street can get very different quotes for a new furnace, and both can be fair. The price depends on your home, your ductwork, the equipment you choose and how the job is done. This guide explains what actually drives the cost of a furnace replacement in Ontario, so you can compare quotes with confidence and spot the ones that leave things out.
Every home is different, so Comfort Zone gives you a clear, written quote after a free in-home assessment. Here is what we look at, and what you should expect any contractor to look at.
1. The Size of Furnace Your Home Needs
Furnace size is measured in BTUs, and the right size comes from a heat loss calculation, not a guess or the size of the old unit. Insulation, windows, ceiling height, air leaks and how many rooms you heat all change the number. A furnace that is too big costs more up front, short-cycles and wears out sooner. One that is too small runs constantly and still leaves cold rooms.
What to ask: did the contractor measure your home, or just read the label on the old furnace?
2. Efficiency Rating (AFUE)
AFUE tells you how much of the fuel becomes heat in your home. A high-efficiency gas furnace turns about 95 to 98 percent of its fuel into heat. Higher efficiency usually costs more to buy and less to run. In a cold Northumberland winter, the savings on your gas bill add up year after year, so the cheapest furnace to buy is not always the cheapest to own.
3. Single-Stage, Two-Stage or Modulating
A single-stage furnace is either on full or off. A two-stage furnace runs on a lower setting most of the time, which is quieter and more even. A modulating furnace adjusts in small steps to match exactly what your home needs. Each step up costs more and gives you steadier temperatures, better humidity and lower energy use. Lennox makes furnaces at every level, so we can match the equipment to your budget and comfort goals.
4. Ductwork, Venting and Gas Lines
The furnace is only part of the job. Older homes in Cobourg, Port Hope and the surrounding towns often need some work before a new furnace can run properly.
- Ductwork that is undersized, leaky or poorly balanced
- A new PVC vent for a high-efficiency furnace, which vents through the side wall instead of the chimney
- A chimney liner if a water heater is left alone in an old chimney
- Gas line changes, a condensate drain or a new electrical connection
- Return air upgrades so the furnace is not starved for air
A good quote lists these items clearly. A quote that skips them may look cheaper, then grow once the job starts.
5. Switching Fuel Types
Moving from oil, propane or electric baseboard to natural gas or a heat pump changes the scope. Oil tank removal, a new gas service from Enbridge, or electrical upgrades for a heat pump all affect the total. Some of these switches also qualify for rebates, which can bring the cost down a lot.
6. Add-Ons That Change the Quote
- A new smart thermostat
- Central air or a heat pump installed at the same time
- Whole-home humidifier or air purifier
- Upgraded filtration or UV lights
- Removal and disposal of the old equipment
Installing a furnace and air conditioner or heat pump together often saves on labour compared with doing them in separate visits.
7. Installation Quality and Warranty
Two quotes for the same furnace can differ because of how the job is done. A proper install includes permits where required, a gas pressure and combustion check, airflow and temperature rise testing, and warranty registration. Ask how long the parts and labour warranties are, who registers them, and what happens if something goes wrong in year one. At Comfort Zone, every install is backed by our six written guarantees.
8. Rebates and Ways to Pay
Rebates can lower your cost significantly, especially if you are adding or switching to a heat pump. Ontario’s Home Renovation Savings Program and the new national heat pump rebate are explained on our rebates page. You can also pay monthly using NGL instead of paying everything up front. And until December 1, 2026, we are offering $1,000 off qualifying Lennox furnaces.
Repair or Replace?
If your furnace is over 15 years old, needs frequent repairs or your bills keep climbing, replacement is often the better value. If it is younger and the problem is a single part, a repair may make more sense. We will tell you honestly which way the evidence points. Read more in Repair or Replace Your Furnace? How to Decide.
How to Compare Furnace Quotes
- Is the furnace size based on a heat loss calculation?
- What is the AFUE, and is it single-stage, two-stage or modulating?
- Are venting, ductwork, gas and electrical work included?
- Are permits, removal and disposal included?
- How long are the parts and labour warranties, and who registers them?
- Which rebates apply, and who handles the paperwork?
Frequently Asked Questions
Why don’t you list furnace prices online?
Because a price without seeing your home is a guess. Size, venting, ductwork and fuel type change the job. A free in-home assessment gets you an accurate, written quote with no surprises.
How long does a furnace replacement take?
Most straight swaps are done in one day. Jobs that include ductwork changes, a fuel switch or a heat pump can take longer, and we will tell you up front.
Is a high-efficiency furnace worth it?
In most Ontario homes, yes. The higher purchase price is usually recovered through lower gas bills over the life of the furnace, especially with our long heating season.
Can I get a rebate on a new furnace?
The biggest rebates right now are for heat pumps, including hybrid systems that pair a heat pump with a gas furnace. See our rebates page for current programs.
Get an accurate quote for your home. Call 289-205-3815 or request your free in-home assessment. We serve Cobourg, Port Hope, Brighton, Colborne, Grafton Campbellford, Quinte West, Belleville, Peterborough and all of Northumberland County. No heat right now? See our 24/7 emergency furnace repair. Learn more about furnace installation.