Solar stills are essential for harnessing solar energy to produce potable water, particularly in arid regions where access to clean water is limited. This study focuses on extending a mathematical model using Response Surface Methodology (RSM) to predict and optimize the efficiency of traditional and stepped solar stills. Key design parameters—including water level, water flow rate, and cover glass thickness—were systematically analyzed for their impact on peak hour efficiency. Extensive data collection was conducted under various operating conditions to inform the RSM model, which produced a predictive equation accounting for complex interactions among input variables. The findings reveal that the peak hour efficiency of stepped solar stills is higher than that of traditional stills. Significant parameters were ranked as follows: solar still type, water level, cover glass thickness, and water flow rate. Interactions between water level and cover glass thickness, along with quadratic effects, significantly impacted efficiency. The model showed high accuracy, achieving an adjusted coefficient of determination of 99.02% and a coefficient of determination of 99.35%. Optimal conditions for maximum efficiency were identified as a stepped solar still with a cover glass thickness of 4 mm, a water flow rate of 15 kg/h, and a water level of 10 mm, yielding predicted and experimental efficiencies of 21.90% and 22.14%, respectively. The regression error of 1.08% indicates the high precision of the RSM model. This approach effectively streamlines the evaluation of solar still design variables, enhancing efficiency optimization efforts.