Effects of electrode size and electrode gap on electrolysis of seawater were studied. As shown in Tables 2 and 4, using a half-sized electrode (T7) significantly decreased chlorine production, electric current, and thus energy consumption of the system, however, its electric efficiency and current effi-ciency were not significantly affected. Results also indicated that increasing the electrode gap to 12 cm (T6 in Table 4) significantly decreased chlorine production and electric current of the system without affecting its electric efficiency and current efficiency. Therefore, the practice of using a small electrode and/or setting a wider electrode gap can be adopted without increasing energy consumption when slow generation and/or low-level chlorine seawater is to be produced.