Particle accumulation increases the pressure drop and reduces the long-term performance of micro-electrostatic precipitators (MESPs). This study quantifies wet-spray regeneration responses for a single MESP geometry intended for residential ventilation. The effects of spray pressure, spray angle, nozzle-to-module distance, and washing duration were evaluated using single-factor and orthogonal experiments. Increasing the spray pressure from 0.1 to 0.3 MPa decreased the post-cleaning pressure drop from 38.5 to 16.5 Pa and increased the pressure recovery rate from 54.9% to 95.3%, while further increases produced diminishing benefits. The operating ranges identified for nozzle-to-module distance and washing duration were 50–100 mm and 20–30 s, respectively. Within the selected factor levels, the factor order was nozzle-to-module distance > spray pressure > washing duration > spray angle. The preferred parameter combination identified by orthogonal range analysis was 0.4 MPa, 30°, 50 mm, and 30 s, based on the factor-level means. This combination requires confirmation using the same module and dust-loading conditions. The numerical comparison gave a relative deviation of 5.5% at 0.3 MPa and provided flow-field context for the parameter trends. The findings link the four spray parameters to residual airflow resistance and post-cleaning particle-collection efficiency, providing operating data for residential MESP regeneration.