The use of a solid polymer electrolyte (SPE) in an anode/SPE/cathode sandwich has emerged as a promising electrochemical configuration to reduce the terminal voltage and thus energy consumption during electrolysis. This study for the first time investigates and compares the efficiency of the electrochemical chlorine production process as well as estimates and compares energy consumption with and without a SPE assembly in the electrolytic cell. Results indicate that at the same current density of 12.5 mA/cm(2), Cl-2 production rate and instantaneous current efficiency (ICE) were higher when no SPE was used than with a functional SPE, most likely because the SPE occupied one side of the electrode surface, thus limiting the contact of Cl- with its surface to generate Cl-2. However, increasing the current density to 31.25 mA/cm(2) with a functional SPE resulted in an almost equal Cl-2 production rate to that at 12.5 mA/cm(2) without a functional SPE, and still the energy consumption per mass of produced Cl-2 was the same, although lower ICE was achieved. The study also further investigated the effect of flowrate, and the influence of initial Cl- concentration and the initial pH for the system with the functional SPE.