Abstract. Energy eﬃciency is an important technology of sensor networks development. In this paper we oﬀer a method of sensors lifetime maximizing under required level of network reliability. The optimizing statement is oﬀered. As example, we consider homogeneous sensor networks with topology like tree. Other example concerns ZigBee technology. It shown that heterogeneous network can be improved by power elements reassignments. If a sensor network topology is ﬁxed then the most critical nodes can be detected and improved.