Abstract— This paper presents an approach to determine the total owning cost (TOC) of transformers. Different assumptions are introduced by discounting the transformer cost and/or the losses cost, using either A and B loss coefficients or the idea of annuity factor. Moreover, the paper presents a comparative study between different cases under different presumptions to evaluate the transformer’s TOC. The obtained results confirm that the proposed approach equips the decision-maker with valuable and trustable criteria to select the proper transformer(s) based on the proposed practical cost criteria. The presumptions of the proposed cost criteria influence economic evaluation. The TOC of the transformer is also illustrated. Finally, the proposed approach cost criteria were illustrated through a numerical example. The obtained results have been summarized and discussed.