Electrolysis of aqueous sodium chloride has been widely used in the chloro-alkali process, and its operating parameters are well-known. This electrochemical mechanism can be applied to both on-site chlorine production for disinfecting water in small-scale drinking water treatment plants and as a portable chlorine generator for emergency use or for campers. However, the design information and operating parameters affecting the current efficiency and power consumption of small-scale electrochlorination systems are limited even though these systems have become popular. We investigate the significant design and operating parameters affecting current efficiency and power consumption in an electrochlorination system. IrO2 electrodes, NaCl concentration, current density, a separator, and temperature control were selected as the design and operating parameters in the two-electrode batch system. The results show that the most important parameter affecting current efficiency and power consumption of chlorine generation was NaCl concentration. At low NaCl concentrations (1000 mg/L), the type of anode, current density, and the separator considerably affected current efficiency and power consumption to generate chlorine, whereas at high NaCl concentrations (>35,000 mg/L), anode type became insignificant, with current efficiency >90% and power consumption of 4-6 Wh/g.