The growing need for renewable energy sources has highlighted the importance of technologies that can bridge the generation-demand gap in the energy system. Thermal Energy Storage (TES) can help to smooth out peaks in energy demand, thereby reducing waste resulting from excess capacity during offpeak periods. Due to their widespread use, significant effort has been dedicated to optimizing the control logic of TES components to maximize the harvested-to-stored energy ratio. The aim of this study is to compare MIX number and dimensionless exergy, two parameters commonly used to identify the storage’s ability to generate and maintain optimal temperature stratification. The investigation is conducted by comparing the parameter response to the thermo-fluid dynamic variations inside the store under several inlet temperatures and flow rates, using a two-dimensional CFD model validated on experimental data collected from an operating commercial stratified tank. The sensitivity of the two performance indicators in detecting stratification losses that are due to different charging conditions is compared, to better understand the applicability of the latter as control parameters during operational phases. Results show that the derivatives of such indicators are less sensible to the tank starting conditions and can be more robust indicators during the charging phase.