The deformability of droplets in an emulsion, when they approach each other, may affect the stability of emulsion and its phase behavior. In this study we have modified the repulsion potential function between the droplets in order to take this phenomenon into account. Appropriate changes to other parts of the potential function have been made to implement the influence of the geometric alternations due to droplets deformation. We have used the first order Barker-Henderson perturbation theory to derive a thermodynamic model for computing the equilibrium between the emulsified water droplets in oil and the separated aqueous phase. Based on the proposed model, phase diagrams for oil-water emulsions have been determined and the effects of various physical parameters on the equilibrium conditions have been investigated. We have also presented phase diagrams comparing the results considering the drops deformable and non-deformable when they approach each other. The model can favorably lead us to the prediction of the required electric field strength for breaking the stable emulsions. The important physical properties such as the polarity of the droplets, adsorption layer thickness, size of the droplets and interfacial tension are taken into account. The results obtained from the proposed model have been favorably compared with available experimental data. It has been shown that deformation has no effect on the emulsions with relatively large water drops; however, for small droplets the effect of deformation is noticeable and could not be ignored. (C) 2011 Elsevier By. All rights reserved.