In this study, two standalone weather-resistant EDS prototypes were tested in the laboratory to investigate the effect of surface charge on dust removal efficiency. Dust was deposited using a sieve deposition method, and a micro-photomicrography method was used to quantify the dust removal efficiency of the prototypes at various locations on the EDS surface, after a single activation of the EDS, also known as the single-operation mode. Both "dry clean" and "wet clean" were used to prepare the EDS surface prior to each experimental run. The method of cleaning prior to the experiment affected the dust removal efficiency, apparently because the different cleaning actions led to different conditions of surface charge. Dry clean resulted EDS efficiency than was only 1/3 that of wet clean. Meanwhile, dry clean left more than twice as much negative charge on the EDS surface as wet clean, measured at 6 min after the cleaning action. This laboratory study shows the effect of surface charge on EDS efficiency, and it can be used to explain the location dependence of dust removal efficiency observed in the field study. Further research is needed to better understand the role of surface charge in the performance of EDS and potentially improve the technology.