The interaction energies between an anionic vacancy and Ca2+ as well as Y3+ as impurity ions in ZrO2 + CaO and ZrO2 + Y2O3 solid electrolytes were calculated by the method of molecular statics and the ionic shell model. The migration energies calculated by molecular statics for the anionic vacancy in the limit of low concentrations of the stabilizing oxide are in good agreement with experimental data obtained at temperatures above that of ageing of ZrO2-based electrolytes with 10 mole % of CaO or Y2O3.