In 1971 McClelland obtained lower and upper bounds for the total π-electron energy. We now formulate the generalized version of these bounds, applicable to the energy-like expression E X = Σ n i =1 |x i − x̅|, where x 1 ,x 2 , . . . ,x n are any real numbers, and x̅ is their arithmetic mean. In particular, if x 1 ,x 2 , . . . ,x n are the eigenvalues of the adjacency, Laplacian, or distance matrix of some graph G, then EX is the graph energy, Laplacian energy, or distance energy, respectively, of G.