Feed water heaters are also used as heat exchangers for heating district hot water in cogeneration plants that simultaneously supply electricity and hot water to large residential apartment complexes, as well as in small-scale district heating systems that use waste heat from urban incineration facilities.

Although the structure and heat transfer method are identical to those of a feed water heater, the heat exchanger in this application is referred to as a District Heating Heater (D.H. Heater) to reflect its specific functional role. Single-zone or two-zone-type L.P. Heaters are typically applied in these configurations.