Urban power supply systems are objects of non-continuous development. Last years due to economic crises load growth has slowed or stopped altogether some years. Despite this, the ongoing reconstruction of the elements of urban power system and networks and new construction in a small volume. The electric loads’ calculations of cities, its reģions and microdistricts are necessary for rational choice of power supply system’s parametres, like substation’s power, its devices’ technical characteristics, cross sections of cabeles and wires, protective devices and so on. It is an important factor for projecting and explitation any objects to ensure a rational development and functioning of networks. In the conditions of initial information’s uncertainty rated load of cities or its regions is determined only by generalized factors. In the work four load definition’s orientating methods of city’s network’s elements are examined and analysed: method for specific rated load in communal and social sector and in terms of population, method for specific consumption of electricity in communal and social sector and in term of population, method for specific rated load in communal and social sector and of building teritory’s living area, method for average load density and building teritory’s area. In the work methods are examined into concrete example – new dwelling microdistrict „Rumbula” of Riga city. In the first conditions of initial information’s uncertainty microdistrict’s orientating total load is defined. Substation’s nominal power is chosen. Substation of 2x32MVA power is recommended to built. Method for average load density and of building teritory’s area is recommended for load definition. The others methods must be used for check of results.