What is a tankless water heater?

A tankless water heater, also called an on-demand or instantaneous water heater, heats water directly as it passes through the unit rather than keeping a supply of hot water ready in a storage tank. When you turn on a hot water tap, water flows through a heat exchanger where a heating element (gas burner or electric element) quickly raises the temperature to your set level before it reaches the fixture.

This design differs fundamentally from conventional tank water heaters, which continuously maintain a tank full of heated water, losing energy through standby heat loss even when you are not using hot water. Tankless units eliminate this waste by producing hot water only when needed.

Tankless systems typically occupy less physical space than storage tanks, making them suitable for homes or properties where space is limited. They also provide a steady stream of hot water, though flow rate varies depending on the unit's capacity and the incoming water temperature. Most models are fueled by natural gas or propane, though electric versions exist for smaller-demand applications.

The technology has become a common choice in Ontario renovations and new construction. If you are considering whether a tankless system suits your home's hot water needs, local plumbers specializing in water heater services can assess your property and advise on sizing and installation.