The economical operation mode is an operation mode in which the loss of transformers in the substation is least. The substation can run in the economical operation mode by means of a series of switching motions. It is worth noting that the substation does not simply obtain energy-saving benefits from a reduction in loss but also there is the cost of switching motions. Therefore the profit from energy saving should be the difference between the two. This paper analyzes both their respective causes and meanings， demonstrates the specific calculation process， and finally gives an example of calculating the energy saving profits that provides an important reference to a certain specific switching motion series in the substation.