An approach is proposed to the choice of overhead line cross-sections that would be optimal under market conditions. For this purpose, in the design practice and at network reconstruction two methods exist: of the economic current density, and of the economic intervals. As of now, none of them works properly, since the cost of electrical materials, of building and construction as well as the total investments in a line are determined by the market prices. Therefore, a modified economic intervals’ method has been developed that can work under market conditions. The method allows also considering the discrete character of standard cross-sections for the lines and concrete technical and technically-economic parameters. For practical application of the proposed method, universal economic nomograms for 20-110-330 kV overhead lines have been calculated and constructed. In the paper, a user interface is proposed for realization of the modified method in Matlab environment.