The separation performance of K+ ions from KCl solution has been investigated by electrodialysis at constant voltage mode of operation as a function of flow rate and voltage scanned. TS-1-10 model electrodialysis equipment (Tokuyama) modified with rotameters was employed in experimental runs. The efficiencies of each unsteady state run were evaluated as specific power consumption with the electrical energy consumed only in stack. The separation performance of K+ ions was compared with that of Na+ ions.