Before you start
Gather a few facts about your home. How many people live there? How many showers might run at once on a busy morning? Where is the current heater, and is natural gas available? How is the existing unit vented? Answers to those questions narrow the choice considerably.
| Consideration | Tank model | On-demand model |
|---|---|---|
| Supply of hot water | The stored volume, followed by a reheating pause | Unbroken, capped by the unit's flow rating |
| Room needed | Occupies floor area in the mechanical room | Wall-mounted, compact |
| Purchase and installation | Usually the cheaper start | Usually dearer once venting and gas sizing are counted |
| Maintenance | Annual flush | Periodic descaling, especially with hard water |
| Standby loss | Some heat lost from the stored water | Minimal |
Step by step
- Estimate peak demand. Count fixtures that run at the same time. Two showers plus a dishwasher needs a high flow rate from a tankless unit.
- Check the gas supply. High-output tankless heaters require a larger gas line than many existing tanks use.
- Look at venting. Tankless gas units use dedicated vent piping, usually through a side wall.
- Consider water hardness. Hard water in Peel means scale inside heat exchangers; a softener reduces that.
- Think about ownership. Many local homes rent their heaters, and rental terms affect the economics.
- Compare lifespan. Tankless units typically last longer than tanks when maintained.
Mistakes to avoid
- Sizing by bedroom count alone. Bathing habits matter more than the number of rooms.
- Ignoring the gas line. An undersized supply causes temperature swings.
- Expecting instant hot water. Tankless units still need time for water to travel from heater to tap.
- Neglecting maintenance. Unserviced tankless units lose efficiency.
A worked example
Consider a family of four with two bathrooms upstairs. On weekday mornings, two showers often run at once while the dishwasher finishes its cycle. A conventional tank sized for that household might handle the morning but run short if a third shower follows. A tankless unit sized for two showers would supply continuous hot water, provided the gas line can deliver enough fuel. The deciding factors would then be the cost of upgrading the gas line and adding new venting, set against the lower standby losses and longer service life of the tankless option. Running through your own household in this way usually makes the answer clear.
When to call
Ask for a site assessment when you are close to a decision. We measure the gas line, look at venting options and discuss your usage before recommending anything. Options include tankless installation, replacing a gas tank, plus electric water heater installation. Where scale is a concern, see water softener installation. Homeowners preparing for storms may also find our notes on basement floods and backwater valves worth reading.
Worth knowing
Answers our Mississauga crew gives most
Does on-demand heating always save energy?
No stored water means no standby loss, yet the saving in practice rests on your consumption and on regular descaling.
Can a tankless heater supply a large family?
Yes, if sized for peak flow. Very high demand may call for a larger unit or two units.