ICT accounts for approximately 2% of world CO2 emissions, a figure equivalent to aviation, according to Gartner estimates. In the remaining 98% software counts for both operationalizing the private sector in doing its business and the public sector in supporting the society, as well as delivering end-user applications that permeate personal life of individuals and families. Software can contribute to decrease power consumption (i.e. become greener) in at least two ways. First, by being more energy efficient, hence using fewer resources and causing fewer CO2 emissions. Second, by making its processes more sustainable, i.e. decreasing the emissions of governments, companies and individuals. To this end, enterprise software must be rethought to address sustainability issues and support innovative business models and processes. The special theme of the second edition of GREENS is “Leveraging energy efficiency to software users.” GREENS 2013 brings together software engineering researchers and practitioners to discuss the state-of-the-art and state-of-the-practice in green software, as well as research challenges, novel ideas, methods, experiences, and tools to support the engineering of sustainable and energy efficient software systems.