Quick answer
Verify TSSA gas licensing and liability insurance, confirm they pull permits, and get itemized written quotes from two or three companies. Good contractors size equipment with a heat-load calculation rather than guessing, offer a workmanship warranty alongside the manufacturer's, and have a track record of reviews mentioning the same technicians by name. Be wary of door-knockers, pressure tactics, and quotes dramatically below the others.
To choose a good HVAC contractor in the GTA, check three things before comparing a single price: a TSSA gas licence held by the person doing the work, proof of liability insurance and WSIB coverage, and a written habit of pulling municipal permits. Installation quality decides how a furnace performs far more than the badge on the cabinet, and Ontario's long history of door-to-door furnace-rental schemes makes the vetting worth an evening.
Non-negotiable credentials
- TSSA gas licence — in Ontario, anyone working on gas appliances must hold a valid Gas Technician licence (G2 or G1). Ask for it; legitimate techs carry their card — why licensing and insurance matter.
- Liability insurance and WSIB coverage — protects you if something goes wrong on your property
- Permits — furnace and AC replacements require municipal permits in most GTA cities; the contractor should pull them, not ask you to skip them
- ODP/refrigerant certification for anyone handling AC refrigerant
Five questions to ask on the first phone call
- Who exactly will be in my basement, and what licence do they hold? A company name on a van is not a technician's credential.
- Do you pull the permit yourselves, and is it a line item on the quote? In Burlington, Oakville and Hamilton that goes through the city or town building department.
- How do you size equipment — a heat-loss calculation, or the label on the old furnace?
- What is your labour warranty in years, in writing — and who answers the phone in year five?
- Is the price flat-rate, and does it include venting, condensate, electrical hookup, disposal and a commissioning test?
What separates good from adequate
- Heat-load calculation — a proper contractor measures your home (or at minimum reviews square footage, insulation, and windows) before naming a size. 'Same size as the old one' repeats any original sizing mistake. See what size furnace you actually need.
- Itemized written quotes — equipment model numbers, venting, permits, disposal, and warranty terms in writing, not a single bottom-line number
- Workmanship warranty — 1–2 years on labour in addition to the manufacturer's parts warranty
- Reviews that mention specifics — repeated technician names, punctuality, cleanup, and post-install follow-up are stronger signals than star count. Read what GTA homeowners say about ZK Mechanical.
- They service what they sell — companies with a real maintenance and repair operation will still answer the phone in year five
Red flags
- Door-to-door sales or unsolicited 'free furnace inspection' calls — the classic Ontario rental-contract trap
- Quotes 30–40% below everyone else — usually missing permits, proper venting, or licensed labour
- Pressure to sign today for a 'one-day price'
- Cash-only, no written contract, or reluctance to show licensing
- Condemning your furnace on the spot without showing you evidence (a crack, a measurement)
How to read three quotes side by side
- Model numbers, not just brand and tier — 'Lennox high-efficiency' is a sales phrase; a model number is a quote you can look up.
- Capacity in BTU, and the heat-loss figure it was based on. Two quotes at different sizes for the same house means at least one of them guessed.
- Venting and condensate spelled out: the two-pipe PVC run, where the termination lands relative to grade and windows, and where the condensate drains.
- Permit, disposal of the old unit, and a startup combustion test as line items.
- Warranty registration — who files it and by what deadline — plus the contractor's own labour warranty in years.
- Rebate paperwork: who files it, and whether the quoted price already assumes the rebate arrives.
Questions homeowners ask while comparing
- Is a bigger company safer? Not by itself — size buys a call centre, not a better installer. Ask who is actually on the truck and how long they've been there.
- What does 'TSSA-registered contractor' mean? Businesses doing gas work register with TSSA as fuels contractors, and their technicians hold individual licences. Ask for both numbers.
- Are online reviews reliable? Read the three-star reviews and the company's replies. A review that names the technician and describes the fix beats any star average.
- How many quotes are enough? Three, from contractors you contacted yourself. Five burns evenings without changing the decision, and the outlier low bid is usually missing a permit or licensed labour.
- Should the quote visit cost anything? No — installation and replacement quotes are free across the GTA; only repair diagnostics carry a fee.
Use the quote process as a test drive
How a company handles a free quote predicts how it handles a warranty call: Did they measure, or eyeball? Did they explain options at multiple price points without pushing the top one? Did the quote arrive when promised? ZK Mechanical has served the GTA for over 15 years with licensed technicians, upfront flat-rate pricing, and free in-home quotes — we're happy to be one of your three estimates.