Should You Replace Your Furnace and AC at the Same Time? Tips for Ontario Homeowners
When your furnace is making strange noises in February, or your AC barely makes it through a humid July in Toronto, the first instinct is often to fix or replace the unit that’s causing the problem. But there’s a bigger question many Ontario homeowners eventually ask:
“If I’m already replacing my furnace (or my AC), should I just do both at the same time?”
It’s a fair question, and one that doesn’t always have a simple answer. Sometimes it makes perfect sense to upgrade both heating and cooling systems together. Other times, it might be better to wait.
This article explores when it’s smart to replace your furnace and AC together, what the cost and efficiency trade-offs are, and how to make a decision based on your home, your budget, and your long-term plans.
Why Replacing Both Systems at Once Can Be the Smarter Move
There’s a reason many HVAC contractors recommend a combo replacement , and it’s not just to sell you more equipment. When your furnace and AC are both over a decade old, replacing them together can often:
- Reduce total installation costs
- Ensure system compatibility
- Increase long-term energy efficiency
- Give you full warranty coverage across both systems
- Minimize service disruptions (only one install day needed)
Many homeowners also prefer getting the upgrade done in one shot instead of facing another big replacement a year or two later.
How Old Are Your Furnace and AC Units?
Start by checking the age of both systems. A well-maintained furnace typically lasts 15–20 years in Ontario homes. AC units usually last around 10–15 years. If both are older than 10 years, or one is failing and the other is getting close, it’s worth seriously considering a combo replacement.
If you’re not sure how old your systems are, your HVAC tech can check serial numbers during your next tune-up or free consultation.
Furnace and AC Compatibility: Why It Matters
Today’s HVAC systems are engineered to work together. That includes:
- Airflow calibration
- Blower speed synchronization
- Smart thermostat integration
- Staging logic (single-stage, two-stage, variable-speed)
If you install a high-efficiency AC but pair it with an old single-speed furnace, it may not perform at its rated SEER efficiency. Likewise, a modern variable-speed furnace won’t function properly with a mismatched outdoor unit.
So if you’re investing in a newer system, make sure your existing equipment isn’t holding it back.
You can explore current furnace models and AC units to see how today’s equipment is designed as part of a matched system.
Real-World Example: GTA Homeowner Upgrade
One of our customers in Vaughan recently replaced their 17-year-old furnace after a no-heat call in January. A few months later, the 15-year-old AC failed during the first heatwave. The two separate installs ended up costing them more , not just in labour and parts, but in multiple site visits, lost time off work, and two system compatibility headaches.
A combo install would’ve saved over $1,200 in total and eliminated the second round of disruption.
The Cost Difference: One vs. Both
Let’s compare average installed costs in Ontario:
| System Replacement | Estimated Cost Range |
| Furnace only | $4,000 – $6,000 |
| AC only | $3,500 – $5,500 |
| Furnace + AC combo | $7,500 – $11,000 |
Savings tip: Most homeowners save $1,000–$1,500 in labour, parts, and ductwork adjustments when doing both together.
Pros and Cons of Replacing Both Systems at Once
| Pros | Cons |
| Lower total cost (vs. two separate installs) | Higher upfront investment |
| Better system compatibility and performance | May replace one unit earlier than strictly needed |
| Full warranty protection on matched components | Some rebate programs may apply to one system only |
| Less home disruption overall | Not ideal if you plan to sell the home soon |
How Long Will a New Furnace and AC Last?
With proper sizing and professional installation:
- New furnaces typically last 15–20 years
- New AC units last 10–15 years
- Combo replacements often come with 10-year parts warranties
Doing both at once resets your home’s HVAC life cycle , and eliminates the guesswork and service calls for the next decade or more.
FAQ: Common Questions from Ontario Homeowners
Q: What if my furnace is old but my AC is only a few years old?
In that case, it may not make sense to replace the AC yet , unless you’re switching to a system like a heat pump, where the indoor and outdoor units need to match. We can evaluate your system during a consultation.
Q: Can I get rebates for replacing both?
Yes. Programs like HER+ in Ontario offer rebates when upgrading heating and cooling systems , especially when switching to heat pumps or high-efficiency models. (Your HVAC contractor must be certified.)
Q: Will a new AC or furnace save me money right away?
If your current system is over 15 years old, a high-efficiency upgrade can reduce heating/cooling bills by 15–30% annually , especially if you install a matched system.
Q: Which brands should I look at for dual replacements?
Check out our comparison of Lennox, and Goodman furnaces , it’s a good place to start if you’re comparing warranties, features, and noise levels.
Final Thoughts: Should You Replace Both Together?
You don’t need to replace your furnace and AC at the same time , but if your systems are aging, mismatched, or inefficient, doing both together might be the most cost-effective and future-proof solution.
You’ll get:
- Better performance and energy savings
- Matched system compatibility
- Lower installation costs
- Full system warranties
- One clean install , no extra disruptions
Whether you’re ready to upgrade or just want advice based on your current system, we’re here to help.
Want to know if it makes sense for your home?
Talk to an HVAC expert for a no-pressure consultation. We’ll help you weigh the options, understand rebates, and plan the upgrade on your schedule.