The public procurement system in Poland remains highly centralized, although thanks to European Community directives, it is part of European law. Therefore, it has established procedures for sustainable public procurement, including so-called green public procurement. In addition to the Public Procurement Law of 11 September 2019, other provisions introducing specific instruments (e.g., energy labels, environmental labels) should be taken into consideration, as such provisions make it easier for contracting authorities to take environmental aspects into account in tender procedures. Bearing in mind the existing legal regulations, this article features a diagnosis of the degree of use of measures to improve energy efficiency in public procurement procedures and models activities related to improving this situation. For this purpose, surveys were conducted for 120 entities applying the provisions of the Public Procurement Law. Taking into consideration the results obtained in the survey, 15 factors related to the improvement of energy efficiency in tender procedures were selected with the help of 12 purposively selected experts connected with the issues raised in this article. Thanks to their expert knowledge, three key factors determining the wider use of this instrument were modeled by means of the systems theory−based methodology of network thinking. The paper also attempts to indicate the key factors determining the wider use of this instrument, using the network thinking methodology for this purpose. As a result of the conducted research, it was found that these factors include human capital, industry, and the energy crisis. Research on the subject in the Polish literature remains innovative and allows for the formulation of application recommendations for decision makers. The concept of energy efficiency in this paper refers to the ratio of the results obtained to the energy input. Efficient use of energy aims to reduce the amount of energy needed to deliver products and services.