This paper presents a method for estimating the useful output of solar D.H.W. system. Heating load calculations, climate data and various conditions are used in this procedure to assess the fraction of the monthly solar energy and the actual solar energy supplied by solar energy for particular system. The design procedure presented in this paper referred to the f-Chart Method. The results of analyzing of this study by Fortran programming are as follows ; 1 . The amount of actual solar energy required to the hot water system is slowly rised to the ascend of tilt angle within the range of $45^{circ}$, with is decreased since $45^{circ}$. 2. The fraction of solar energy is superior when collector area is $8.64m^2$. 3. At the tilt angle with the range of $37.6^{circ}~45^{circ}$, the amount of actual solar energy established the best results. 4 Both the fraction of solar energy and the actual solar energy are the most suitable during the storage volume is $300{iota}$.