How does a tankless water heater work?

A tankless water heater mounted on the outside of a home.

A tankless water heater, also known as an on-demand water heater or instantaneous water heater, works by heating water directly as it flows through the unit, without the need for a storage tank. Here's how it operates:

1. Water Flow Initiation: When hot water is needed, the homeowner or occupant opens a hot water tap in the house, initiating the flow of cold water into the tankless water heater.

2. Heat Exchanger Activation: Inside the tankless water heater, a heat exchanger, typically powered by either gas or electricity, activates in response to the flow of cold water. The heat exchanger is the key component responsible for heating the water.

3. Water Heating Process: As cold water flows through the heat exchanger, it is heated almost instantly to the desired temperature. The heating process occurs as the water passes over heating elements (for electric tankless heaters) or through a burner (for gas-fired tankless heaters). The heat source rapidly heats the water to the set temperature as it flows through the unit.

4. Continuous Flow: Tankless water heaters provide hot water on demand, meaning they can continuously supply hot water as long as there is a demand for it. Unlike traditional water heaters with storage tanks, which can run out of hot water and require time to reheat a new tankful, tankless water heaters provide a continuous supply of hot water.

5. Temperature Regulation: Tankless water heaters typically come with controls that allow users to set the desired temperature of the hot water. This allows for customized comfort levels and energy efficiency.

Key advantages of tankless water heaters include their space-saving design, energy efficiency, and unlimited hot water supply. However, they may have higher upfront costs compared to traditional water heaters, and the flow rate can be limited if multiple hot water fixtures are used simultaneously.

Overall, tankless water heaters provide an efficient and convenient solution for delivering hot water on demand while minimizing energy consumption and maximizing space utilization.