Let G be a graph with n vertices and m edges. In this project, we establish some bounds on energy of graph based on n and m. Two graph with the same number of vertices are called equienergytic if they have the same energy. In this project, we introduce some classes of equienergetic graph. A graph of order n is called hyperenergetic ht energy of graph greater than 2n-2. In the end, it is shown that Keneser graphs and their complement are hyperenergetic.