The proper dimensioning of distribution transformers is an issue of paramount importance for the design of electrical distribution networks with high standards of efficiency and quality of energy. In this paper we propose a methodology for the analysis of load states in the different nominal capacities of single-phase distribution transformers. The main objective of this analysis is to achieve a mathematical model that allows the analysis of feasibility to perform the replacement of an existing transformer in the network with a known state of load, by another selected transformer with efficiency criteria that contributes to the reduction of technical losses in electrical distribution networks. The implementation of the feasible model of optimal transformer utilization will be analyzed with the exhaustive search algorithm under the criteria of limit load index relation, according to the known load conditions for a given transformer. The results will be validated in a real study case, with measurements in a single-phase distribution transformer and the simulations of the exhaustive search model will be done with the help of the Matlab software, verifying the energy efficiency analysis with the adequate replacement of existing transformers by optimal transformers proposed in the model.