The way of estimating the costs of the electrorefining of copper and of selecting the optimum electrolysis current density has been presented. The analysis has been carried out for the flow electrolyser taking into account the capital costs, electrical energy costs, heating or cooling costs and the electrolyte pumping costs. Against a background of the present literature data the values of the above-mentioned cost coefficients have been estimated and the optimum current densities determined, and also the economic reasons discussed. The method presented does not depend on the system scale.