## 1 Introduction  
The European Commission through actions, decisions and interventions in recent years is encouraging public authorities to make their purchasing decisions \"greener\". Public procurement is a key aspect of public investment as it stimulates economic growth worldwide [1]. The respective expenditure represents around 14% of EU GDP [2] and GPP is an approach that supports public authorities to achieve environmental benefits through the procurement process. EU defines GPP as \"a process whereby public authorities seek to procure goods, services and works with a reduced environmental impact throughout their life cycle when compared to goods, services and works with the same primary function that would otherwise be procured\" [3]. GPP stands out as a fundamental market instrument for achieving EU governance goals regarding environmental change, asset utilization and sustained use and creation--especially given the importance of the current energy crisis and the fiscal constraints imposed by many governments. GPP enlarged implementation will help to maintain EU's leadership in environmental performance [4]. The European Commission has made several attempts to promote the use of green rules in public procurement. Directives 2004/17/EC and 2004/18/EC, which were replaced by directives 2014/24/EU and 2014/25/EU respectively, are considered important interventions in the application of green criteria in public procurement. Legally binding prerequisites must take into account rules such as reduced capital outflows, unrest, reduced asset utilization, etc. [5]. In 2010, most EU countries effectively transformed EU mandates into a public ordinance and National Action Plans (NAPs) were drawn up based on GPP. Specific product groups were identified in order to be used for the implementation of GPP, such as construction, office IT equipment, cleaning products and services and copying and graphic paper [6]. According to European Green Deal Investment Plan (COM 2020), the European Commission will propose further legislation on GPP, with minimum mandatory green criteria or targets for public procurements. Under this green investment plan, public authorities across Europe will be encouraged to integrate green criteria and use labels in their procurements. At the same time, European directives encourage the purchasers in public services to use LCC methodologies whenever possible [7]. Directive 2014/24/EU encourages the use of LCC within the public procurement process as there is an entire article on life-cycle costing, highlighting its importance in the context of green procurement. Moreover, a variety of existing LCC tools deals with financial, environmental and social concerns [8]. Considering the previous and despite the fact that there is an increasing interest of researchers in green procurement [9; 10; 11; 12], the understanding and adaptation by public purchasers of both economic and environmental objectives in the procurement of goods and services remains optional [13]. This paper explores the relationship between GPP and LCC and evaluates the economic impact of green procurement through the application of LCC tools developed by the EU in green procurement projects in the Greek public sector. Through this evaluation, it is determined whether green products have by default a higher investment cost than non-green ones. Thus, the aim of this paper is to evaluate the results of the LCC tools implementation in the context of GPP in Greece and study the economic impact of green procurement in public organizations. The urgent need of reducing energy consumption in the public sector due to the continuing energy crisis and climate change is an additional incentive to evaluate this impact. The remainder of the paper is structured as follows: in Section 2 the current state of GPP in Europe and in Greece is presented, with a brief literature review on the LCC implementation in public procurement. Section 3 presents the LCC implementation in the case of GPP in Greece.