In this research paper, an attempt has been made to unearth the effect of different thicknesses glass cover on passive single-slope single basin solar still in winter climatic conditions of Mehsana (23°12’ N, 72°30’) from September, 2010 to Feb. 2011. Experiment used three identical size solar stills having three different thicknesses of glass cover of 4 mm, 8 mm and 12 mm. Here, Dunkle model is used for comparison of various heat transfer coefficients of solar stills. The objective of the present paper is to evaluate the behavioral variation in various parameters on solar still. Six month study shows that, lower glass cover thickness gives increase in distillate output, water temperature, evaporative heat transfer coefficient, convective heat transfer coefficient as well as efficiency of solar still. Hence, 4 mm glass cover thickness is most prominent thickness of present experiment.