The shape of capsulation and geometric design play an important role in saving and raising the efficiency of the solar cell modules. The measurements of power were carried out for poly-Si solar cell modules in two modes, horizontal and full tracking on the roof top of building in our Institute (NRIAG) in Helwan (Lat. 29 degrees 52＇ N; Long. 31 degrees 20＇ E) which is considered as the largest polluted region in the world. The data measurements are carried out from sunrise to sunset through one full year from January to December 1992. The daily and monthly variation for different components of solar cells are studied and discussed. The difference between the two modes in the gain energy is 84% (about 34% as the natural difference between the horizontal and full tracking, and 50% by the defect of design of solar cell module).