Rooftop units heat and cool most of the GTA's commercial space — retail, offices, restaurants, warehouses — and they sit out of sight on the roof until the day a tenant calls to say it's 29°C inside. The good news: nearly every RTU failure is preventable with a simple, cheap maintenance rhythm. Here's the one that keeps them running.
What an RTU is and why it fails
A rooftop unit (RTU) is a self-contained HVAC package — fan, coils, compressor, and often a gas heat section — mounted on the roof, ducting conditioned air down into the space below. It's exposed to everything the roof is: sun, rain, snow, wind-blown dust, and in restaurant settings, grease-laden exhaust. That exposure is exactly why RTUs need consistent attention.
Almost every RTU failure comes from one of a short list of causes:
- Clogged filters — restrict airflow, strain the fan motor, and cut capacity. The cheapest and most-skipped fix.
- Worn or slipping belts — reduce airflow and eventually snap, stopping the unit entirely.
- Dirty condenser coils — the unit can't reject heat, so cooling capacity drops and the compressor runs hot.
- Electrical failures — capacitors and contactors are common failure points; a $40 capacitor left unreplaced can take out a compressor.
- Seized economizer dampers — stuck open wastes energy; stuck closed loses free cooling. Economizers are notorious for failing unnoticed.
- Clogged condensate drains — overflow that can leak into the ceiling below.
The pattern that turns a cheap problem into a capital cost: a clogged filter or dirty coil makes the unit work harder → the compressor runs hotter and longer → months later the compressor fails. A $30 filter and a $200 coil cleaning prevent a $4,000–$8,000 compressor replacement. RTU maintenance is almost entirely about catching the cheap problems before they become the expensive ones.
The RTU maintenance schedule
| Task | Frequency |
|---|---|
| Filter replacement | Every 1–3 months |
| Belt inspection & tension | 2× / year |
| Condenser & evaporator coil cleaning | 1–2× / year |
| Refrigerant charge check | 1× / year |
| Electrical connections & capacitor test | 2× / year |
| Economizer operation test | 2× / year |
| Condensate drain clean & flush | 2× / year |
| Gas heat section & safety check | 1× / year (pre-heating) |
The two anchor visits are spring (pre-cooling) and fall (pre-heating). Restaurants, buildings near construction or industrial sites, and high-traffic retail should run filters monthly and consider quarterly full service — their units foul far faster.
When to repair vs. replace an RTU
| Replace when… | Repair when… |
|---|---|
| Past 15–20 years old | Under 12 years old |
| Compressor or heat exchanger failed | Failure is a replaceable part |
| Uses obsolete R-22 refrigerant | Uses current refrigerant |
| Single repair > ~50% of replacement | Repair is a fraction of replacement |
The R-22 line is the one that catches people. Units made before the mid-2010s often run R-22, which is phased out — the refrigerant is expensive and getting scarcer. A major repair on an R-22 unit often means pouring money into a machine you'll replace soon anyway. For those, replacement with a current-refrigerant, higher-efficiency unit is frequently the better economic call.
What RTU replacement costs in the GTA (2026)
| Unit size | 2026 installed cost |
|---|---|
| 5 – 7.5 ton | $12,000 – $25,000 |
| 10 – 15 ton | $22,000 – $40,000 |
| 20 – 25 ton | $45,000 – $80,000 |
| Crane lift (varies by height/street) | +$3,000 – $15,000 |
Against those capital numbers, maintenance is trivial: a twice-yearly RTU program runs a few hundred dollars per unit per year and routinely adds 5+ years of life while keeping energy use down. The buildings that skip maintenance to save a few hundred dollars are the ones paying $30,000 for an emergency replacement three years early.
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Request a Free Assessment →Frequently Asked Questions
How often should a commercial rooftop unit be serviced?
At least twice a year — spring before cooling and fall before heating — with filters changed every 1–3 months. Restaurants and dusty environments benefit from quarterly full service. Each visit covers filters, belts, coils, drains, refrigerant, electrical, and economizer operation.
What is the most common rooftop unit failure?
Clogged filters, slipping belts, dirty condenser coils, failed capacitors/contactors, and seized economizer dampers. Most are cheap to fix during maintenance but become expensive compressor or motor failures if left unaddressed.
When should a rooftop unit be replaced instead of repaired?
Replace if it's past 15–20 years, the compressor or heat exchanger failed, it uses obsolete R-22, or a repair exceeds ~50% of replacement cost. Repair if it's newer and the failure is a replaceable component. R-22 units are often worth replacing outright.
How much does a commercial rooftop unit cost to replace in the GTA?
In 2026: roughly $12,000–$25,000 (5–7.5 ton), $22,000–$40,000 (10–15 ton), $45,000–$80,000 (20–25 ton), installed — plus $3,000–$15,000 for a crane lift. Twice-yearly maintenance extends unit life and defers these costs.