The paper focuses on the development strategies in Latvian largest city (Riga), systematization of its existing infrastructure and load density formation. Well-founded approach to the future loads' definition on early stages of longterm planning and medium-term design is offered. The development process at district and microdistrict of large city is mainly provided by growth of load and according to load density. Reliable information about such an important parameter as load density can be used to help with the future loads of new district, preliminary selection of loads' elements of electrical systems, installed powers of transformers and placement of new transformer substation (TS). In this paper the question of formation, determination and update of load density on different voltage levels in large city is presented. Moreover, the determination of future substations' loads on the basis of load densities in city districts is considered.