In this study, a time-integrated performance index (TIPI) was proposed to assess the compromise between amounts of removed metallic ions (RMI) and the consumed electric energy (CEE) in wastewater treatment systems based on the electrocoagulation (EC) process. An aluminum electrode-based EC reactor along with a Zn2+ ion-based electrolytic medium was used to assess the effect of electrical conductivity (κ) in low | values (215-415 μS cm-1) was used to highlight κ effects on total electric voltage (UEC) and EC performance. Measurements of metallic ion concentrations, κ and UEC were performed in time. A Nernst-Planck equation-based mathematical model for the time description of κ was proposed. In all EC tests, time-dependent behaviors on κ, UEC and electric current were observed. The κ experimental data were well fitted by the κ model, showing profiles modulated by the time behavior of the metallic ion concentrations. The maximum TIPI value (1.2/Wh) was achieved about 10âmin electrolysis time, dropping quickly due to a substantial reduction (350 to 50 μS cm-1 after 60âmin) in κ and, consequently, an increase in CEE (up to 2 Wh after 60âmin). Thus, this drop in κ value became more evident at the end of shorter electrolysis times related to the low κ conditions driving towards a significant loss in TIPI. In a global context of the EC performance, TIPI has brought another perspective to address in an optimized EC process, looking for the highest values within a steady state.