In this research project two solar still plants have been fabricated; single and double slope still plants. The exergy and exergy efficiency concepts have been applied for the comparative analyses of both solar stills. Experimental readings, i.e. various temperatures, amounts of distilled water and solar radiations have been taken for solar stills at different time intervals in Indore (22° 43′ 4.51″ N and 75° 49′ 59.88″ E). The percentage variations in the different parameters, i.e. increments in temperature, increments in quantity of water, thermal efficiencies, rates of exergy at inlet/outlet and exergy efficiencies have also been calculated for stills at various solar intensities and time intervals. After experimental and comparative analyses, better outputs have been shown at 14:50 PM for double slope and 14:45 PM for single slope plant due to the cumulative effects of solar radiations on the still plants. During this period thermal/exergy efficiencies, i.e. 46.630/1.949% and 47.259/3.389% were found the best. The performance of single slope solar still has been found better, and 14:30 to 14:50 PM time interval has been recorded superior for the distillation of water through still plants where percentage increments of the performance evaluating parameters were enhanced. Keywords Single and double slope solar stills • Thermal efficiency • Rates of inlet and outlet exergy • Exergy efficiency • Solar radiation List of symbols C Specific heat of water (J/kg K) dT w Temperature difference which was achieved due to solar energy (K) I b R B Solar radiation which is available for single and double slope solar still (W/m 2) L Length of the solar still (m) m Mass flow rate of pure water (kg/s) T 0, T w and T s Ambient, water and Sun's surface temperatures (K) W Width of the solar still (m) Greek symbols η Thermal efficiency of the solar still (%) α g , ρ g and τ g Absorptivity, reflectivity and transmissivity of the glass Ψ in and Ψ out Exergy at inlet and outlet for single and double slope solar still (W)