Tankless water heaters are also referred to as combination or “combi” boilers, instantaneous, continuous flow, inline, flash, on-demand or instant-on water heaters. These water heaters heat the water as the water flows through the device, and do not retain the water except for what is in the heat exchanger coil.

tankless water heater are often installed throughout a household at more than one point-of-use. The main advantage of using them is that it provides a continuous flow of hot water and energy savings compared to a limited amount and flow of continuously heating hot water from conventional tank water heaters.