Tankless water heaters, also called continuous water heaters, produce hot water on demand. This stands in contrast to tank water heaters which maintain a reserve of hot water. Tankless water heaters commonly have efficiencies in the range 82% to as high as 97%, in contrast to standard tank water heaters with efficiencies in the range 59-62%. Tankless water heaters also do not experience the standby losses of tanks.
When a user opens the hot water tap, cold water travels into the unit. A gas burner then heats the water continuously as it flows through, before leaving as hot water. Electronic sensors control the gas burner and maintain the desired temperature within a couple degrees of the set point temperature.
In residential settings, tankless water heaters save energy without running out of hot water. Commercial settings can save floor space by using a tankless heater.
III Equipment Options
Tankless water heaters can form part of combined water and space heating systems. Typical residential installations are sized for 3 simultaneous uses of hot water, although other capacities are available. While many heaters are installed indoors, they can be mounted outdoors in warmer climates.
1. Equipment Manufacturer Database
2. Natural Gas Efficiency Consortium