Intermediate voltage 1000 V will make it possible to shorten the lengths of 0,4 kV lines and to improve the quality of electrical energy at consumers. At the same time, the length of 20 kV power lines can be diminished as well which will lower fault probability and raise electrical energy delivery reliability. Besides, medium voltage power lines are more expensive than low voltage ones. According to EU directive LVD73/23/EEC, the 1000 V rated voltage can be assigned to low voltage class and the cost of 1000 V lines raises only slightly as compared with 0,4 kV lines. However implementation of extra voltage nominal requires one transformation step in addition which must be implemented by considerable number of small 1/0,4 kV transformers, which implies additional expenditures in distribution networks as a whole. In each concrete case, the usefulness of 1 kV voltage nominal implementation can be resolved upon only by calculations of economical efficiency. A number of parameters and indices of each involved voltage nominal must be taken into account: the cost of line construction, the price of big and small transformers, pay for electrical energy losses, the failure rate of the lines and equipment, average repair duration and expense, the interruption costs. The calculations make sense only if the chosen variant ensures the electrical energy quality corresponding with accepted norms. The minimum of annual expenses can be attained optimizing the topology of the network. In order to determine the realm of intermediate voltage use, it is necessary to perform a series of calculations, possibly using Monte Carlo method.