The most critical part and barrier of phase change material (PCM) applications are the accuracy of simulations and the control of the process. The state of the PCM and the momentarily stored energy cannot be estimated easily unless numerous temperature sensors are used. There are a lot of models used by researchers, but most of them focus solely on the full charging or discharging of the PCM thermal energy storage. In a real working environment, the phase change is often interrupted so this phenomenon should also be modelled with high accuracy. The aim of this paper is to present the newly developed diagonal model validated by differential scanning calorimetry measurements, which can model what occurs inside the hysteresis of the solid-liquid two-phase state. The model was created and validated by using paraffin wax (P53) and was further tested with coconut oil (C.oil20), which has a very wide hysteresis. The modelling accuracy of the different models was compared with each other, and the evaluations were carried out. Keywords Phase change materials (PCM) Á Differential scanning calorimetry (DSC) Á Enthalpy-temperature curves Á Phase transition Á Interrupted melting/solidification List of symbols c Specific heat capacity (kJ kg -1 K -1 ) c app Apparent heat capacity of the PCM during melting (kJ kg -1 K -1 ) f Liquid fraction of PCM (1) H Enthalpy (kJ kg -1 ) L f Latent heat of fusion (kJ kg -1 ) T Temperature (°C)