Amphipathic alpha-helical peptides, among other peripheral components of plasma membranes, are promising antimicrobial agents. Partial incorporation of a peptide into a lipid monolayer causes elastic deformations. Deformations induced by two peptides distant from each other are independent; when peptides get closer, interference between the deformations causes effective lateral interaction. We quantified the energy of membrane deformations for arbitrary configuration of two amphipathic peptides on the membrane surface. The global minimum of the deformation energy proved to be achieved when two parallel peptides are in registry at the distance of about 6 nm between the axes of peptides. The energy calculated in the unidimensional approach provides a good approximation for the dependence of the energy of peptides being in the registered configuration upon the distance between them, valid for a broad range of peptide lengths. The effective interactional length of peptides for the unidimensional approach is close to their actual length. If two parallel peptides are shifted along their axes with respect to each other, the interaction energy is also well approximated by the unidimensional potential, within the projection of one peptide onto the other. In the case when the axes of alpha helices cross at a substantial angle, the main contribution to peptide interactions comes from their edges: the effective length of peptides for the unidimensional approach is almost equal to the characteristic length of decay of deformations. Based on the results we obtained it can be concluded that interaction of membrane inclusions is quite adequately described by the potential calculated in the unidimensional approach.