Most people don’t think about their water heater until the shower runs cold or there’s a puddle on the basement floor. If yours is getting old, or you’re renovating, it’s worth deciding ahead of time whether to stick with a traditional tank or switch to a tankless unit. Both can be a good choice. The right one depends on how your household uses hot water and what your home can support.
How Each Type Works
A tank water heater stores a set amount of water and keeps it hot around the clock. When you use hot water, cold water refills the tank and gets heated back up.
A tankless water heater (also called on-demand) has no storage tank. When you open a hot tap, water flows through a heat exchanger and is heated as it passes through. When you close the tap, the unit shuts off.
Both types come in gas and electric versions.
Hot Water Supply
Tank: You get a fixed amount of hot water at a time. Back-to-back showers, a bath plus a dishwasher, or a full house of guests can empty the tank, and then you wait while it reheats. Sizing the tank properly for your household matters.
Tankless: You won’t run out of hot water, but there’s a limit to how much it can heat at once. If two showers, the dishwasher and the washing machine all run together, a unit that’s too small can’t keep up and the water gets lukewarm.
That flow limit matters more in the GTA than in warmer places. In winter, the water coming into your home is much colder, so a tankless heater has to raise the temperature further, which typically reduces how much hot water it can deliver at once. A good installer sizes the unit for winter conditions, not summer.
Lifespan
According to the U.S. Department of Energy, storage tank water heaters typically last around 10 to 15 years, while tankless units often last 20 years or more. Real-world lifespan depends heavily on water quality, installation and maintenance. Many tanks fail closer to the low end of that range, and tankless units that are never descaled can wear out early.
Energy Efficiency
A tank loses some heat all day and night, even when nobody is using water. This is called standby heat loss. Because a tankless unit only heats water when you need it, it avoids that loss and is usually more energy efficient, especially in smaller households that use less hot water. For large families with heavy, simultaneous use, the efficiency gap tends to narrow.
Space and Installation
- Tanks take up floor space but are usually a straightforward swap for an existing tank in the same spot.
- Tankless units mount on the wall and free up floor space, which helps in tight basements, condos and finished utility rooms.
- Gas tankless units often need a different venting setup and may need a larger gas supply line than an old tank used.
- Electric tankless units can draw a lot of power, and some homes need electrical upgrades before one can be installed.
Switching from tank to tankless is usually a bigger job than replacing a tank with a tank, so get a proper assessment before deciding.
Safety note: Any work on the gas line, gas valve, burner or venting of a gas water heater must be done by a licensed gas technician. Never try to disconnect or reconnect a gas supply yourself. Electrical work on an electric unit should be left to a qualified professional as well.
Maintenance
- Tank: Draining a few litres from the bottom once or twice a year helps clear sediment. Testing the temperature and pressure relief valve occasionally is also recommended. Follow the manufacturer’s instructions.
- Tankless: Most manufacturers recommend periodic descaling (flushing the heat exchanger) to remove mineral buildup. Many units also have an inlet filter that needs cleaning.
Quick Comparison
| Tank | Tankless | |
|---|---|---|
| Hot water supply | Limited by tank size | Continuous, limited by flow rate |
| Typical lifespan | About 10 to 15 years | Often 20+ years |
| Standby heat loss | Yes | No |
| Space needed | Floor space | Wall-mounted, compact |
| Switching over | Simple tank-for-tank swap | May need venting, gas or electrical changes |
Which One Should You Choose?
A tank often makes sense if you want a simple replacement in the same spot, your household’s hot water use is predictable, or your home would need major gas or electrical work for a tankless unit.
A tankless unit often makes sense if you’re short on space, plan to stay in your home for many years, want to cut standby energy loss, or regularly run out of hot water with your current tank.
If your current water heater is rented, as many are in Ontario, check your rental agreement before you replace or remove it.
Signs Your Water Heater Needs Attention
- Rusty or discoloured hot water
- Rumbling or popping sounds from the tank
- Water pooling around the base
- Hot water running out much faster than it used to
- A tank that’s past the typical lifespan range
A leaking tank can get worse quickly. If water is spreading, shut off the cold water supply to the heater and call an emergency plumber. For anything less urgent, our water heater repair and installation team can help you decide whether to repair or replace.
Need a Plumber?
Not sure whether tank or tankless is right for your home? Call Northlife Plumbing at (437) 246-5507 or request a free quote. We install and repair tank and tankless water heaters across North York, Toronto and the GTA, with 24/7 service and upfront pricing you approve before work starts.