This paper is dedicated to the analysis of energy efficiency of the D2D direct connection system in 5G networks. Fast development of 5G networks results in large increase of volumes of the data transmitted by the users. On one hand, the reduction of coverage areas of small cells and increase of their number in places with high load level enhance the capacity and quality of the whole system. On the other hand, increase of density of the network coverage leads to greater complexity of the system. As a result, one requires alternative approaches to improve the communication quality. In the research we suggest to apply direct connection technologies for the improvement of performance of 5G systems. The paper presents the results of numerical experiments and analysis of the dependences of number of users, of the probability of blocking and of the energy consumption on the input intensity of sessions of D2D systems. These results demonstrate improved performance of the 5G network with D2D direct connection compared to LTE systems. Therefore, the application of D2D technology allows to increase the data transfer rates and to improve energy efficiency of 5G networks.