An automatic method for designing housing-estate distribution systems is described which offers a practical and economical alternative to present design techniques. Substation positions and feeding arrangements are calculated instead of being determined intuitively, resulting in better layouts and closer approaches to given engineering limits. The method was applied to four housing estates and achieved savings ranging from 6 to 15% of the m.v. mains expenditure required by the previous manual designs. Apart from capital savings, uniform standards of design are obtained and designers are relieved of much tedious work.The automatic method can facilitate management decisions by supplying cost figures for variations in design. For example, alternative substation sites may be tested when optimum sites are difficult to secure, the cost of increase in assumed a.d.m.d. can be determined and variations in the number of standard cable sizes can be investigated.Special features of the automatic method are the division of irregular estate areas and a road-selection procedure which determines the shortest route between two points.