This study compares the performance of nanosecond pulse (NSP) and direct current (DC) power supplies for use in a municipal wastewater treatment by electrocoagulation (EC). Four Al plates connected in monopolar-parallel configuration (MP-P) were used as electrodes during the EC process. The maximum chemical oxygen demand (COD) removal efficiency reached 68% and 80% using DC and NSP, respectively. Moreover, NSP treatment reduced approximately 15% of the specific energy consumption (SEC) compared with that by DC at a similar COD removal efficiency of ≈ 68%, which was used as a benchmark value. In addition, when using NSP, the SEC required to increase the COD removal efficiency from 60% to 68% was two to three times less than that when DC was applied. The results suggest that an NSP operating at 10 kHz frequency (f) and 1 µs pulse width (pw) are preferred for obtaining higher COD removal efficiencies at a low SEC. The use of an NSP for EC can enhance the COD removal efficiency and reduce the wastewater treatment SEC. The results presented herein promote the use of EC systems combined with renewable energy sources for reducing the net carbon footprint of wastewater processing.