Abstract An experimental investigation is carried out on three unsymmetrical solar stills with different insulation under actual field conditions. Also, a simple economic evaluation of solar distillation is made to find out the best insulating material, in Egypt, to be used in the asymmetrical solar stills. From the experimental results, an empirical correlation for the daily production from the stills is deduced. The results also show that the daily production of the stills increases by about 35% as the mean ambient air temperature increases from 17 to 30°C at the same daily total solar radiation and the same thermal insulation. From an economic point of view, it is found that dry sawdust is the best material, in Egypt, to be used for insulating the asymmetrical solar stills.