The modeling techniques of rare events, which include power or energy shortage when evaluating the reliability of electric power systems by simulation methods, are considered. The main purpose is to investigate the use of iterative methods for forming a sequence of nested probability subspaces, with their decreasing probability. The procedure of the subspace method is realized. A modification of the cross-entropy method is proposed, which consists of a smooth adaptation of the indicator function. A comparison of the discussed techniques is performed. It is shown that the main disadvantage of the considered methods is their efficiency dependence on the proper specification of parametric constants. The means of improving the accuracy and the convergence of iterative procedures are outlined.