Abstract An enhanced TRNSYS simulation model, NEM, of the behaviour of a domestic hot-water (DHW) store, with an immersed heat-exchanger (HX), has been developed and validated. This model simulates the dynamic heat-depletion and recovery processes in the immersed HX and predicts the transient temperature-patterns for various DHW draw-off versus time profiles. Realistic daily profiles (RDPs), based on field studies, were developed to provide representative draw-off patterns for the testing of thermal stores and simulation studies. The effects of these RDPs and five other existing profiles on the store’s performance are analysed using the enhanced model. The simulation results indicate the importance of the HX’s recovery, as well as the number, type and time of occurrence of the draw-offs in the profile, on the thermal store’s performance. It is concluded that RDP profiles should be used in the performance testing of thermal stores to obtain results that reflect conditions experienced in the field.