Tank or tankless for a Calgary basement suite, which fits better?

A standard 50-gallon gas tank water heater supplied and installed runs roughly $1,500 to $3,500 in Calgary; a tankless gas unit costs $2,200 to $5,000 installed, plus $400 to $1,500 more if the gas line needs upgrading. For a basement suite, that gap matters, but so do several practical factors that often tip the decision.

Tank vs. Tankless for a Suite

A tank heater is simpler and cheaper upfront. It works well when the suite has its own dedicated unit, the basement has enough space for the tank and its clearances, and the existing gas line can handle the load. The main drawback in Calgary is hard water: the City's water supply runs roughly 141 to 274 mg/L of hardness depending on which treatment plant feeds your neighbourhood. Sediment builds up faster here than in softer-water cities, so annual flushing is not optional, it is maintenance. A tank typically lasts roughly 8 to 12 years, and neglect in hard water pushes it toward the short end.

A tankless unit delivers hot water on demand and takes up far less wall space, which matters in a basement where mechanical room square footage is tight. The tradeoff is a much higher gas demand while it runs: the existing gas line was sized for the original appliances, and adding a high-output tankless unit can require upgrading to a larger line or adding a dedicated run. Get a gasfitter to assess the existing gas supply before you commit to tankless, because that upgrade alone can add $400 to $1,500 to the project.

Venting is the other variable. A tankless unit usually needs its own venting, often through an exterior wall. In a basement suite that may mean cutting through concrete or navigating finished walls. A conventional tank may be able to use an existing flue if it is the right size and configuration, though that needs to be confirmed on-site.

For a basement suite specifically, also consider whether the suite shares a water heater with the main unit or has its own. A shared tank is simpler to install, but hot water and utility costs then have to be split between households. A dedicated unit for the suite, whether tank or tankless, is cleaner for a landlord-tenant relationship.

Permit rules in Calgary: The City of Calgary does not require a permit for a straight like-for-like tank swap, but a permit is required when the venting changes, when the gas line upstream of the shut-off valve changes, or when the type of heater changes (for example, switching from a natural draft tank to a direct-vent tankless). A homeowner cannot take out a gas permit in Calgary unless they are a certified journeyman gasfitter; the certified gasfitter doing the work takes out the gas permit, and the City inspects the work.

Before hiring, ask the plumber or gasfitter for their trade certificate number, confirm the contractor holds an Alberta prepaid contracting licence if you are paying a deposit, and request a WCB-Alberta clearance letter.

When you get quotes, ask each contractor exactly which permit they will pull, who books the inspection, and what happens if the gas line needs upgrading once the work is open.