The vision of the GAMES project is for a new generation of energy efficient IT Service Centres. With the unprecedented digitisation of business and government processes across Europe, energy efficiency of IT Systems and IT Service Centres is dramatically emerging as one of the most critical environmental challenges to be dealt with. A first yet partial answer to the energy challenges is offered by the emerging IT Service Centre paradigm, in which the available computing resources are shared by several different users. However, current tools and methods for assessing and managing energy efficiency at the IT Service Centre level were designed to operate in isolation, not taking into account all the interrelations between the different layers (business/applications, infrastructure, facility) and the effect of these interrelations on energy consumption. The GAMES project aims at developing a set of innovative methodologies and Open Source ICT tools for designing and managing energy efficiency in IT Service Centres, by combining all the three above layers. This will be done by: 1) delivering a methodology and a web toolset for the holistic design of green IT service centres, trading-off Quality of Service, performance, virtual and physical resource allocation and overall energy efficiency, 2) enriching the GAMES toolset by implementing advanced algorithms for closely aligning applications' demands for power with the resource availability, and combining these algorithms with data mining technologies; 3) complementing these tools and methodology with a run-time environment for integrated sensing, monitoring and adaptive control, capable of assessing in real time to a what extent the implemented course of actions will improve energy efficiency. The main expected outcome will be to increase energy efficiency in IT Service Centres by up to 25%. The effectiveness of the proposed solutions will be validated through extensive real life testbeds located in Italy and Germany.