Abstract. Information Technology is a dominant player of our modern societies; Data Centres, lying at the heart of the IT landscape, have attracted attention, with their increasing energy consumption being a constant topic of concern, especially when it comes to the negative impact on the quality of their surrounding environment. Nevertheless, recent technological and societal advances are paving the way for DCs to change their role from passive energy consumers into prosumers, thus, transforming themselves into leading players within their smart district surroundings. This paper describes the innovative GEYSER approach to enabling green networked DCs to monitor, control, reuse, and optimize both their energy consumption and production, and in particular from renewable resources, towards becoming active participants within Smart Grids and Smart Cities.