Two theoretical approaches-the 2pK triple layer model and the 1pK basic Stern model-describing the charging process at oxide/electrolyte interfaces were applied to analyze the surface charge isotherms and the heats of proton adsorption. The presented analysis was carried out by accepting both the frequently employed model of an energetically homogeneous oxide surface and a more realistic model taking into account the energetic heterogeneity of the actual oxide surfaces. The developed theoretical expressions were applied to analyze experimental data sets reported for three adsorption systems: Al2O3/NaCl, TiO2/NaCl, and SiO2/NaCl. It was found that both the 2pK and the 1pK surface charging models could well describe potentiometric titration curves, and can represent the most characteristic features of the measured enthalpy of proton adsorption. In the case of the 1pK model, introducing the concept of surface energetic heterogeneity does not affect much the fit of the experimentally measured heats of proton adsorption, Best fits were obtained by applying the 2pK model taking into account the surface energetic heterogeneity. These best fits, however, were obtained at the expense of introducing more best-fit parameters. So, the general conclusion is that, for some adsorption systems, the use of the simpler IpK model leads to a sufficiently accurate description of experimental data, whereas, for some other systems, the use of the 2pK model seems to be necessary.