A tankless water heater is a wall-mounted appliance that heats water only as it flows. Opening a hot tap trips a flow sensor, which fires a gas burner that heats water passing through a heat exchanger. With no stored water there is no standby heat loss and no tank to run out, but output is limited by flow rate.
Why it matters to you
Many Fraser Valley homes still run a 40–60 gallon gas tank, and switching to tankless usually means a larger gas line and new venting, which is gas work that needs a licensed gas fitter and a permit in BC. Where water is harder, scale on the heat exchanger is the main threat to a tankless unit.
Practical guidance
Size the unit on how many fixtures you run at once, not on a brochure flow rate. Budget for annual descaling, and get the gas line and venting work quoted alongside the heater itself.
Tankless vs. storage tank water heaters at a glance
| Storage tank | Tankless | |
|---|---|---|
| How it heats | Keeps 40–60 gallons hot around the clock | Heats water only as it flows |
| Hot water limit | Tank volume — can run out | Flow rate — can be outrun, never runs out |
| Standby heat loss | Yes, keeps stored water hot overnight | None, nothing is stored |
| Upfront cost | Lower | Higher, equipment and install |
| Installation | Simpler, often reuses existing venting | Usually needs a larger gas line and new venting |
| Space | Floor-standing tank | Wall-mounted, frees floor space |
| Lifespan | Shorter | Longer — a well-maintained unit often outlasts two tanks |
| Routine maintenance | Annual flush to clear sediment | Periodic descaling of the heat exchanger |
Is a tankless water heater worth the higher upfront cost?
It tends to pay off when your household regularly runs out of hot water, you plan to stay eight or more years, floor space matters, or your tank is already past ten years old. If the budget is tight, the existing venting suits a tank, or it is a rental, a good storage tank is a perfectly rational choice.
Why does switching from a tank to tankless cost more than the heater alone?
A tankless burner needs much more gas at full fire than a tank, so the gas line often has to be upsized, and the unit usually needs new venting. In BC, new or resized gas lines are permitted gas work done by a licensed gas fitter. Those items belong on the quote, not discovered on installation day.
Can a tankless water heater run out of hot water?
It cannot run out the way a tank does, but it can be outrun. A tankless unit delivers a set flow at a given temperature rise, so two showers and a dishwasher at once can exceed a unit sized too small, and the water cools. Correct sizing on your real simultaneous demand prevents this.
What maintenance does a tankless water heater need?
Periodic descaling of the heat exchanger, which matters most where water is harder; skipped for years, scale restricts flow and costs efficiency and lifespan. Annual descaling also commonly supports the manufacturer's warranty terms, so keep the service records.