Phase change slurries (PCS) consist on a carrier fluid binary system, where water is mostly used as continuous phase and micro-encapsulated phase change materials (MPCM) are used as dispersed phase. PCS are used in Thermal Energy Storage (TES) for building applications, combining the latent heat capacity of the MPCM with the sensible heat capacity of the carrier fluid, and at the same time giving the PCM pumpable properties. In this study, two PCS samples are compared and characterized, the commercial Micronal® DS 5007 X from BASF and a laboratory made PCS28. Thereby, in this paper thermal stability is studied by using thermogravimetrical analysis (TGA) and the main components of the MPCM have been studied using Fourier transformed infrared spectroscopy (FT-IR). Moreover, TGA coupled with FT-IR is used to study deeply the thermal decompositions of the PCS microcapsules and products derived thereof. Finally, differential scanning calorimetry (DSC) is performed to study the melting enthalpy and the melting temperature range of the phase change material (PCM). This paper concludes that both types of PCS have good potential from thermal energy storage purposes such as solar space heating applications.