This paper presents the results of a comparison between EPW (Energie Prestatie Wetgeving, i.e., the new calculation method of the Flemish Energy Performance Regulation) and two transient building energy simulation programs: TRNSYS and ESP-r. The Energy Performance Regulation and the three calculation programs are described and their calculated net energy demands are compared to each other and to experimental data from a co-heating test. Considering the steady-state nature of the EPW model, the results of this research are very promising.