When a tank water heater starts leaking, many homeowners ask whether this is the moment to switch to tankless. Sometimes it is. Sometimes a new tank is the smarter, cheaper choice. It comes down to how your household uses hot water, what your gas line and venting can support, and how long you plan to stay.
Here is the comparison we walk customers through before quoting either option.
How each one works
A tank heater keeps 40 to 75 gallons hot at all times. When it runs out, you wait for it to recover. A tankless unit fires a powerful burner only when a tap opens, heating water as it passes through a heat exchanger.
That means tankless never runs out, but it can only heat so many litres per minute. Two showers and a dishwasher at once can exceed what a small unit delivers, especially in winter when incoming water is cold.
Sizing is about flow, not gallons
Tankless units are sized by how many fixtures you run at the same time and how much the water has to be heated. Groundwater in Ontario can be quite cold in winter, so the unit has to do more work then than in summer.
We add up the fixtures your household realistically uses at once and size for winter conditions so you are not disappointed in January.
Installation differences
Replacing a tank with a tank is usually straightforward. Converting to tankless often involves more work, which affects the price.
- A larger gas supply line to handle the higher burner input.
- New venting, often PVC through a side wall.
- A condensate drain on high efficiency models.
- Wall mounting and new water connections.
Running costs and lifespan
Tankless units avoid standby heat loss because they are not keeping a tank hot all day. How much you save depends on your usage. Tankless units typically last longer than tanks when they are maintained, while tanks commonly last around 10 to 12 years.
Rather than quote a payback figure that may not apply to your home, we compare the installed price of both options for your actual setup.
Not sure it's a DIY fix?
Describe the symptom over the phone and a HeatNest technician will tell you what it likely is and what a repair involves.
Call (289) 801-7262Hard water and maintenance
Scale builds up inside a tankless heat exchanger and reduces performance, eventually triggering error codes. A yearly descaling flush keeps it working properly. Tanks also benefit from flushing and anode rod checks, but they are more forgiving.
Which one we usually recommend
Tankless tends to suit households that run out of hot water often, want to free up floor space, and plan to stay in the home. A new tank tends to suit tight budgets, homes where the gas line upgrade would be extensive, or anyone planning to sell soon. We will tell you honestly which fits.
Common questions
+Will a tankless water heater run out of hot water?
No, but it can be overwhelmed if too many fixtures run at once for its size. Proper sizing prevents this.
+Do I need a new gas line for tankless?
Often, yes. Tankless burners need more gas than a tank, and existing lines are frequently too small.
+How long does a tankless installation take?
Most conversions take a full day, depending on gas line and venting work.
+How often should tankless units be descaled?
Once a year in most homes, more often with very hard water.
+Can I keep my tank and add a tankless?
It is possible in some setups, but usually one system sized correctly is simpler and more efficient.