Аннотация:One of the most important topics of sustainability research and applications is reaching energy efficiency. In this paper we analysed more than 100,000 of patents related to different aspects of energy efficiency with the issue dates from 1973 to 2019. In the paper we will discuss how network theory can be applied to discover technology trends and apply them to improve sustainability efforts making more educated decision. This paper will demonstrate how patenting trends change with time and how different topics influence each other.