Energy Efficiency has become more important in recent years. This is shown by the development of engery consumption of information and communication technology (10 % of the german energy consumption in 2007). Futhermore battery development cannot keep up with the ubiquitous and powerful mobile devices. Research on hardware and low level software optimizations has been comprehensively explored. But the research on optimizing energy consumption on application level is still in its infancy. So in this project should be improved Energy Efficiency of applications by using reengineering services, like static and dynamic program analysis, and systematic code transformations.