Polarization deficiency and excess ion hydration free energy at an electric field E (ion hydration free energy at the field E subtracted by the ion hydration free energy at zero field) of hydrated calcium, sodium, and chloride ions have been determined by Monte Carlo simulations. A spherical cell containing either one ion and molecular water or only molecular water subjected to an external electrical field was used. The permittivity of pure water decreases as E is increased, in quantitative agreement with previous simulation studies and the Booth theory. The excess ion hydration free energy depends quadratically on E up to ca. 2.5.10(8) V/m, whereas it becomes linear in E at higher field due to dielectric saturation. The values of the excess ion hydration free energies are in quantitative agreement with measured dependencies of the relative permittivity of electrolyte solution upon the ion concentration. A primitive polarization model of electrolyte solution near charged interfaces is proposed. The use of this model leads to an additional effective repulsive force acting on hydrated ions near charged surfaces and significantly affects the distribution of calcium ions near such surfaces.