Entropy generation for the natural convection phenomena is studied for different geometrical cavities that have identical boundary conditions and unit area. The key characteristic parameter in this study was the Grashof number. The effect of Grashof number on Nusselt number and entropy generation has been studied using finite element method. The developed models in this study were validated against published work in the literature and results were found to be in close agreement. Entropy generation was found to increase with an increase in the Grashof number and the heat transfer was the dominant factor in increasing the entropy generation. A lower entropy generation is generally expected with an increase in the distance between the hot and cold boundaries. It is also noted that the rate of entropy generation decreases slowly when the flow domain is only slightly distorted, while the rate of entropy generation increases sharply when the flow domain changes significantly.