The hybrid character of a solar desalination system consisting of a "greenhouse"- type conventional solar still coupled with a solar collector field and hot water storage tank was investigated. This system shows significantly higher distilled water output compared with that of an uncoupled still, and moreover has the advantage of supplying hot water from its storage tank. Through experimental data taken from system operation in the laboratory, the suitability of the developed "input-output" method, was proven for reliable description of the system operation. It was shown that the model previously developed is capable of estimating long-term distilled water production with deviation not higher than 3% for any considered period. Following this, a theoretical investigation of hybrid operation of the system is performed concerning reduction of produced distilled water caused by storage tank hot water draw-off of different volumes at the end of the day. The results show that draw-off of hot water volume equal to 1/4, 1/2 or 1 tank volume reduces distilled water output by 36%, 57% or 75%, respectively, by simultaneous energy output of about 1900, 3300 and 5200 MJ. From the results, the characteristic curve describing the behavior of the hybrid system was drawn, which can be used during the design phase or during usage of the system.