German energy utility company N-ERGIE is expanding its district heating network with a 15 to 20MW (4,265 to 5,686TR) isobutane (R600a) heat pump that will supply heat to roughly 5,000 homes in Nuremberg using heat from treated wastewater.

In 2024, the Nuremberg Department of Sewage and Environmental Analysis (SUN) treated 71 million cubic meters (18.7 billion gallons/70.7 billion liters) of wastewater at the city’s treatment plant on Adolf Braun Street. The treated water is discharged into the Pegnitz River, with a consistent temperature between 13 and 20°C (55.4 and 68°F). With the treated wastewater as a heat source, the heat pump will produce up to 120°C (248°F) hot water for the district heating network.

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