A tankless water heater costs $3,500–$6,500 installed in the GTA, and the most common job — a mid-tier 199,000 BTU gas unit from Rinnai or Navien replacing an existing tank — lands at $4,200–$5,000. A straight tank-for-tank swap runs $1,200–$2,500, so you are paying roughly double up front for endless hot water, a 15–20 year service life instead of 8–12, and the floor space back. Here is what actually drives the number on your quote.
What a GTA tankless install costs, line by line
- Mid-tier condensing gas tankless replacing an existing tank: $4,200–$5,000 installed — the standard GTA job
- The full band across brands, capacities and awkward mechanical rooms: $3,500–$6,500
- Gas line upsizing from the meter: an extra $400–$1,200 where the existing run can't feed the unit
- Venting, condensate and electrical work on a difficult location: $300–$1,000 on top
- Annual descale flush thereafter: $150–$300
What a proper install includes
- The unit, sized on flow rate rather than on the tank it replaces
- Stainless or PVC direct-vent kit and a concentric termination through the wall
- Gas connection and a pressure test on the finished piping
- Hot and cold water connections, with isolation valves so the unit can be descaled without draining the house
- Condensate drain and neutraliser on condensing models
- A dedicated 120 V circuit — a tankless unit is electronics plus a fan, and it does nothing without power
- Removal and disposal of the old tank
- Permit and inspection
- Workmanship warranty in writing alongside the manufacturer's
The gas line is what moves the price
This is the single biggest surprise on a tankless quote, and it is arithmetic rather than upselling. A standing tank fires at a fraction of what a tankless unit draws, because the tank has hours to reheat and the tankless has seconds. Older GTA homes were piped for the tank, so the run from the meter — and occasionally the meter itself — has to be resized to CSA B149.1 before the new unit will hold its rated output on a cold February morning.
Upsizing that run adds $400–$1,200. A contractor who surveys the piping during the in-home visit puts it in the written quote; one who doesn't will find it on install day, when your options are worse. Ask specifically what size the existing run is and what the new unit needs.
Tank versus tankless, side by side
- Installed cost — tank $1,200–$2,500 · tankless $3,500–$6,500
- Typical service life — tank 8–12 years · tankless 15–20 years
- Running cost — tankless saves roughly $80–$200 a year against a standing tank, because nothing is being reheated while you're at work
- Space — a tank occupies a corner of the mechanical room · a tankless hangs on the wall in about the footprint of a carry-on
- Maintenance — tank: anode rod and an annual flush · tankless: a descale flush at $150–$300
- Hot water — a tank gives you a finite volume and then cold · a tankless is limited by flow rate, so it never runs out but it can run thin if too many fixtures open at once
- Power failure — an atmospheric tank with a standing pilot keeps making hot water · every tankless needs its 120 V supply and stops when the power does
Free quotes, written pricing.
Our tankless versus tank comparison goes deeper on the comfort trade-offs; this page is about the money.
There is a third column plenty of GTA houses are actually in: renting. At $25–$45 a month with annual increases, a rented tank costs roughly $4,500–$8,000 over a 15-year span, against $1,500–$3,000 to own the same class of unit outright. Before comparing tankless to tank, compare renting to owning — our guide on renting versus buying a water heater covers the buyout and removal mechanics.
Sizing is about temperature rise, not household size
Tankless capacity is rated in litres per minute at a given temperature rise, and that rise is what changes between July and February. Municipal water entering a Burlington or Hamilton house in late winter is close to freezing, so a unit sized around a mild-weather rise delivers noticeably less flow when you actually want a hot shower. Size on the winter case and on your real simultaneous demand — two showers plus a dishwasher is the usual design point. See what size tankless water heater you need.
When tankless isn't the right buy
- One- and two-person households where standby loss on a tank is small and the payback stretches past the equipment's life
- Gas service that can't be upsized at sensible cost — a long run from a meter at the far corner of the house
- Hard water with no softener and no intention of descaling; scale on a tankless heat exchanger is the fastest way to shorten its life
- An emergency replacement where the tank has already failed, the basement is wet, and hot water is needed today rather than after a permit and a gas-line change
- Homes that lose power often and have no generator, where a standing-pilot tank has a genuine resilience advantage
Maintenance, hard water and what neglect looks like
Water across Halton and Hamilton is moderately hard, and a tankless heat exchanger is a narrow passage the water moves through quickly — which is exactly the geometry that collects scale. An annual descale flush through the isolation valves at $150–$300 keeps rated output where it belongs; skip it for years and you get longer waits, temperature swings mid-shower and error codes for flow that isn't there. Cleaning the inlet screen filter takes two minutes and belongs on the same visit.
Get a real tankless quote
ZK Mechanical installs gas tankless units across Burlington, Oakville, Hamilton and the wider GTA, and the gas-line survey happens during the quote rather than on install day. See our tankless water heater service, check financing options if you'd rather spread the cost, or request a written quote.
Frequently asked questions
How much does a tankless water heater cost installed in Toronto?
Installed prices in Toronto and the wider GTA run $3,500 to $6,500 depending on brand, capacity and how much the mechanical room fights back. The common configuration — a mid-tier 199,000 BTU gas unit from Rinnai or Navien replacing an existing tank — lands at $4,200 to $5,000. Gas-line upsizing and long venting runs are what push a quote toward the top of the band.
Does a tankless water heater pay for itself in the GTA?
Over the equipment's life, usually, for households of three or more who plan to stay put. The running-cost saving is $80 to $200 a year, and a 15 to 20 year service life against 8 to 12 for a tank means one purchase instead of two. For a one- or two-person household, or a home you expect to sell inside five years, the arithmetic lands close to even.
What's the lifespan of a tankless water heater?
A well-maintained gas tankless unit runs 15 to 20 years, against 8 to 12 for a typical tank. The variable is descaling. Water across the GTA and Hamilton is moderately hard, and scale builds inside the narrow passages of a tankless heat exchanger far faster than it does in a tank, so an annual flush is the difference between the top and bottom of that range.
Do tankless water heaters need a bigger gas line?
Frequently, yes. A tankless unit draws far more gas at once than the tank it replaces, because it heats on demand instead of over an hour, and most older GTA homes were piped for the tank. Resizing the run from the meter to CSA B149.1 adds $400 to $1,200. A contractor who checks the piping during the quote puts that in writing rather than raising it on install day.
Can I install a tankless water heater myself?
No. Connecting gas piping and commissioning a tankless unit in Ontario is restricted to a TSSA-licensed technician, and the dedicated 120 V circuit falls under ESA rules. Beyond the legal problem, self-installed gas work voids the manufacturer's warranty, shows up in a pre-sale inspection, and gives an insurer an opening to argue about a claim.