Abstract: Evaluation of Transformer Owning Cost (TOC) plays an important role during the selection of a transformer by an industrial customer. The dependency and the relationship between the transformer design and the TOC is used to obtain a cost optimal design for the test case. The TOC evaluation by conventional method is compared with those of results obtained after optimizing design variables using Genetic Algorithm (GA) and Particle Swarm Optimization (PSO), out of which the latter has provided a much minimized solution than the other two methods. Thus a minimized total owning cost is obtained using design variables optimized by particle swarm optimization technique.