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This study comprehensively evaluated the performance of 3D printed electrodes with different lattice structures (Cubic, Diamond, Schwartz, and SplitP) in microbial electrolysis cell-assisted anaerobic digestion (MEC-AD) systems under various power supply conditions (24 h ON, 18 h ON, 12 h ON, and 6 h ON). The shortest startup time (2 days) and the highest biomethane production (534.8 ± 30 L/m3) under continuous power supply mode (24 h ON) was achieved by SplitP-MEC-AD, which possessed the largest surface area, but it achieved the lowest current density generation and biomethane production under intermittent power supply modes (18 h–6 h ON). The computational fluid dynamics analysis revealed that SplitP-MEC-AD experienced significantly high turbulence (turbulent kinetic energy = 0.86141 m2/s2, max fluid velocity = 2.95 m/s), which may have hindered the cathode biofilm combined with unfavorable intermittent power supply conditions. The highest current densities were always achieved by Cubic-MEC-AD, which had the lowest resistance. Diamond-MEC-AD (larger surface area and lower resistance) achieved the highest biomethane generation (411.4 ± 53.7 L/m3) during the intermittent power supply. Cathodic microbial communities differed significantly among MEC-ADs, possibly due to varying geometries. Our research indicates that both Cubic and Diamond electrodes are suitable cathode choices for MEC-AD systems with further modifications. [Display omitted] • 3DP cathodes were comprehensively evaluated in MEC-AD under various power schemes. • SplitP-MEC-AD achieved the highest biomethane with a continuous power supply. • Cubic and Diamond provided the highest methane productivity under on/off mode. • CFD analysis emphasized the role of high turbulence in deteriorating performance. [ABSTRACT FROM AUTHOR]