Electroreflectance of Cu, Ag and Au single crystal surfaces in contact with an aqueous electrolyte is briefly reviewed and discussed. It is shown that surface states at the metal - electrolyte interface contribute significantly to the overall electroreflectance effect, and they can provide information on the electric field distribution inside the electrochemical double layer. Infrared electroreflectance may be used to detect contributions from the double layer constituents directly. Finally, the role of non-local optics for interpretation of electroreflectance spectra is emphasized