The article discusses a novel approach, the 'chemical potential method,' as an alternative to the conventional van’t Hoff method for determining reaction enthalpies and entropies in processes like the thermochemical reduction of oxides. By utilizing the oxygen chemical potential ΔμO instead of oxygen partial pressure pO2, this new method separates the contributions of the probe gas and the solid-state properties of oxides, offering a clearer insight into their applicability for specific uses. The study evaluates three model systems to demonstrate the efficacy of this method, including generic oxides, alloys with interacting vacancies, and charged vacancy formation in CeO2. Through this analysis, the article highlights the importance of understanding the temperature dependence of reduction enthalpy and entropy in deciphering defect mechanisms. The exceptional behavior of CeO2 in thermochemical water splitting cycles is emphasized, showcasing the impact of defect ionization. Furthermore, the article explores the potential of the charged defect mechanism in enhancing the efficiency of solar thermochemical hydrogen production, using variations of the CeO2 model parameters to assess theoretical performance limits.