Large Hot Water Tank for waste heat at city cleaning Hamburg

The installation of a hot water tank from Haase was worthwhile for the Hamburg city cleaning (SRH). After converting the heating system, the previously unused waste heat from the server room is now being used. This is used to heat shower and drinking water and also supports the heating system. At the same time, the effective use of waste heat ensures the previously complex cooling of server operation. By renewing the system, city cleaning Hamburg was able to save 500,000 kilowatt hours and thus 81 tons of CO2 last year. That roughly corresponds to the heating requirements of 90 modern terraced houses.

The majority of the hot water is consumed daily between 1 p.m. and 3 p.m. by the approximately 500 employees in waste collection, city cleaning and workshops. Then 68 showers are in full swing. While the hot water tank is fed with waste heat from the server room 24 hours a day, the hot water is discharged in just two hours. This fact requires a comparatively large hot water tank. The Haase large storage tank has a volume of at least 30,000 liters and was specially tailored to the requirements of city cleaning. Standard hot water tank with 1,000 or 2,000 liters capacity would not be up to the task.

The installation room is difficult to access, which is why only on-site installation and thus the large Haase storage facility were considered.

Technical drawing of the hot water tank of the city cleaning Hamburg.
Technical drawing of the hot water tank

Graduate engineer Dominik Iskenius-Eggers, who has supervised the project from the start, sums up how successful this investment is for Hamburg’s city cleaning: “This example thoroughly disproves the frequently used argument ‘ecology does not pay off’. The hot water requirement can be met all year round via the data center, so that the heating network can be switched off completely in summer, “continues Iskenius-Eggers.

The climate protection officer of the SRH, Dr. Stefan Lübben, continues: “The project was more successful, the savings were much higher than we had expected.” In this way, the previous calculations could be corrected with a payback period of ten years to around three years.


  • Filling volume: 30,000 liters
  • Height: 2.80 m
  • Diameter: 4.40 m


  • 25,000 liters hot water a day
  • Energy savings of 500,000 kWh per year
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