The choice between a condensing and non-condensing gas tankless unit has a direct impact on installation cost and complexity. Non-condensing units exhaust hot gases (around 300°F) and require stainless steel or Category III metal venting, which is expensive and must be routed to an exterior wall or roof. Condensing units extract additional heat from those exhaust gases, producing cooler exhaust (around 100°F) that can be vented through inexpensive PVC or polypropylene pipe — much easier and cheaper to route.
The trade-off: condensing units cost more upfront (typically $300–$800 more for the unit), but the venting savings often close that gap or reverse it entirely. Condensing units also produce acidic condensate that needs to be drained — usually to a floor drain or neutralisation trap. If your installation location doesn't have easy drain access, factor that into the plan.
A whole-home gas tankless heater draws significantly more BTUs during operation than a storage tank (which fires at a lower, sustained rate). Many older Canadian homes have gas lines sized for a tank — typically ½-inch supply. A tankless unit may require a ¾-inch or even 1-inch gas line from the meter, depending on BTU input and the length of the run. If the gas meter itself is undersized, you'll need to coordinate with your gas utility (Enbridge, FortisBC, etc.) for an upgrade — which can add weeks to the project timeline. (If you're budgeting a larger renovation alongside a water heater swap, be aware that tariffs on US-sourced materials may affect appliance and hardware costs through 2026.)
Even gas tankless units need electricity — typically a standard 120V outlet on a dedicated circuit for the electronic ignition, controls, and fan. This is a minor requirement. Electric whole-home tankless heaters are a different story entirely: they may need 150+ amps across multiple dedicated 240V circuits, which often exceeds the spare capacity on Canadian residential panels.
In Ontario, any gas appliance installation must be performed by a contractor registered with the Technical Standards and Safety Authority (TSSA). This is not optional — it's provincial law. The installing contractor must tag the unit with a compliance sticker and file the appropriate documentation. If you're modifying gas lines, electrical panels, or structural venting penetrations, municipal building permits may also be required depending on your municipality.
The Government of Canada has warned homeowners about misleading door-to-door sales tactics for water heaters and furnaces, including salespeople who misuse EnerGuide or ENERGY STAR branding. NRCan does not offer direct product rebates — but it maintains a searchable directory of legitimate regional efficiency programs through utilities and provincial governments.
Before you approve any tankless installation quote, confirm these specifics in writing:
This checklist isn't paranoia. It's the difference between a $3,500 project and a $6,000 surprise.
