At a glance
- 01
Never runs out
Back-to-back showers, a big tub and the dishwasher, without waiting for a tank to recover.
- 02
Space back
The unit hangs on the wall. The floor space where the tank stood is yours again.
- 03
Sized by flow, not gallons
The contractor sizes it on how many fixtures run at once in a Hamilton winter.
- 04
Longer life
Tankless units often last 15 to 20 years with yearly descaling.
How tankless works
A tankless water heater does not store hot water. When you open a hot tap, a flow sensor fires a powerful gas burner, and water passes through a heat exchanger and comes out hot a few seconds later. When the tap closes, the burner stops. Because nothing is kept hot between uses, there is no standby loss, and because the burner can keep going, it does not run out. A tankless water heater is the most common upgrade for families who fight over the last hot shower.
Sizing: it is about flow
A tank is sized by how many gallons it holds. A tankless unit is sized by how many litres a minute it can heat at a given temperature rise. That rise is larger in winter: incoming water in the Hamilton area can be well under 10 °C in February, and it needs to be raised to about 50 °C at the shower. The contractor adds up the fixtures likely to run at once, typically two showers plus a tap, and sizes for that on a winter day. An undersized unit gives lukewarm showers when two are running.
Gas line and venting
A tankless burner is large, often 150,000 to 199,000 BTU/h, compared with 40,000 for a typical tank. Many houses need a larger gas line from the meter, and the meter itself sometimes needs upgrading by Enbridge. Units vent through PVC or polypropylene pipe to an outside wall, like a high-efficiency furnace. Those two items are why tankless installation costs more than a tank swap, and a good quote spells them out.
Tankless vs tank
- Up-front cost: a tankless install usually costs $4,000 to $7,000, roughly double a tank.
- Running cost: lower, because there is no standby loss. The saving is real but modest for a small household.
- Lifespan: often 15 to 20 years, against 8 to 12 for a tank.
- Hot water supply: endless, within the flow rate. A tank runs out and needs time to recover.
- Power cuts: a tankless unit needs electricity for its controls and fan, so no power means no hot water. Some conventional tanks keep working.
Our guide to tankless vs tank water heaters goes through the choice in more detail.
Hard water and maintenance
Much of the Hamilton area has moderately hard to hard water, and scale builds up in a tankless heat exchanger over time, reducing its output and eventually causing errors. Units should be flushed with a descaling solution once a year, which needs isolation valves fitted at installation. A water softener or a scale-reduction filter extends the time between flushes.
Where it goes
Most tankless units hang on a basement wall near where the old tank stood, so the cold and hot water lines stay short. The venting needs to reach an outside wall with the right clearances from windows, doors, the gas meter and the ground, and from a neighbour’s window on a narrow lot. In winter the exhaust plume is visible and the condensate needs a drain. Units on a long run from the bathrooms take longer to deliver hot water, and a recirculation pump or a small buffer tank can fix that if waiting bothers you.
Combi boilers: tankless plus heat
In homes heated by hot water, a combination boiler can do both jobs: it heats the radiators and makes on-demand hot water from one wall-hung unit. See boilers and radiant heating.
Leaving a rented tank
If your current tank is rented, switching to an owned tankless unit means returning the rental tank under the terms of your agreement. Ask the rental company about the process and any fees before installation day. Our rent vs buy guide covers what to check.
Who can install one
Gas tankless water heaters are fuel-burning appliances, so the installation, gas line and venting must be done by a TSSA-certified gas technician working for a registered contractor.
How the request works
You request a tankless quote once, and we pass it to one licensed contractor who works your area. Say how many bathrooms you have, how many people live in the house, whether the current tank is rented, and where the gas meter is in relation to the utility room.
Typical prices
CAD · before GST/HST
- Gas tankless, replacing a tankIncluding new venting
- $4,000–$7,000
- Gas line upsizing, if needed
- $300–$1,200
- Yearly descaling and service
- $150–$250
Typical 2026 installed prices in Hamilton and the surrounding area, before HST and before any rebate. They are a guide, not a quote: the contractor you are matched with sets the price after seeing the home.
Questions people ask
How much does a tankless water heater cost to install in Hamilton?
Usually $4,000 to $7,000 installed, before HST, including new venting. A larger gas line or a meter upgrade adds to it.
Will a tankless water heater run two showers at once?
A correctly sized unit will. The contractor sizes it for the number of fixtures that run at the same time, using winter water temperatures.
Does a tankless water heater need maintenance?
Yes. It should be descaled once a year, more often with hard water, and the air intake and filter screen cleaned.
Is tankless worth it for a small household?
For one or two people with modest hot water use, the energy saving is small and a good tank is often the cheaper choice. Tankless pays off best for larger families and long showers.