The energy consumption in an apartment building in Copenhagen supplied by district heating has been monitored from November 2000 to June 2002. During the period heat cost allocators were installed on the radiators and the set point for domestic hot water was raised in order to prevent the Legionella Disease. Results from the space heating system and the loading circuit for production of domestic hot water are discussed with respect to heat loads, cooling of the district heating water and the efficiency of the pump and the heat exchangers. The Public Service Obligation for utility companies in Denmark to help their customers to save energy calls for tools to analyse the energy consumption and the efficiency of the system. The possibility to use three-dimensional plots to analyse the thermodynamic performance is discussed as one option. (C) 2004 Elsevier B.V. All rights reserved.