In recent years, due to the increasing demand for electricity, and at the same time aimed at reducing environmental pollution during electricity production, the world has been turning to the production of electricity from renewable sources, and thus the Republic of Croatia. In addition to reducing environmental pollution, the goal is to reduce network losses due to the transmission of electricity produced from the point of production to the point of consumption, and smaller production plants are being built close to the consumption, which are connected to the distribution network. Distributed electricity generation occurs. The distribution networks to which the distributed sources are connected are undergoing major changes and are being given a new role for which they were not originally dimensioned and need to be further built and equipped in order for the distributed sources to be connected to them. Distributed sources have a significant impact on the level of technical losses in distribution networks, so that they can affect the reduction as well as the increase of losses, which depends on the technical solution of the connection and the consumption of electricity at or near the place of production. The topic of this paper is an analysis of the assessment of the impact of connection of distributed sources on distribution networks, and the valorization of the criteria of technical losses in the selection of technical solutions for connection of new sources.