Obtained expressions for the network at chosen nominal voltage renders possibility to consider the per unit cost of the network and other quantities at various nominal voltages. More fully the problem can be treated for network of two voltage levels (low voltage and medium voltage level) together, getting the summary costs. The per unit costs weakly increases with the higher (relatively to investigated zone) voltage level; the cost altogether weakly increases changing the size of the zone; strongly increases with investigated zone voltage if power line costs heavily depend on the said voltage; strongly decreases with load density and distance between consumers (disposition) increasing. This last feature causes the cost of low voltage zone to be higher than that of medium voltage zone. Active and reactive voltage drop in low voltage fed zone increase along with optimum zone size by increasing the medium voltage and decrease when load density and disposition grows; in medium voltage zone they behave differently by load density increasing: real drop decreases, imaginary grows; they both increase with disposition and decrease with medium voltage increasing. Matching the low voltage zone with medium voltage zone, it should be kept in mind that the cost is much stronger depends on loads disposition than on zone size. Power line cost increase with voltage influences the number of nominal voltages. There is not significant difference in costs when line cost weakly depends on voltage. Otherwise, the important reason should be for the increase of nominal voltage. It can be assumed that some of the nominal voltages in the range of 3 – 20 kV and 20 – 110 kV can be excluded.