Energy-efficiency and power consumption of applications has become a major topic in High Performance Computing in the last years. This poster presents the work of the last two years in the eeClust project1. The aim of the project is to reduce the energy consumption of applications on commodity HPC clusters with as little performance impact as possible by an integrated approach of application analysis, efficient management of hardware power-states and monitoring of the clusters power consumption. We outline the overall project plan and present the generation and analysis of traces on application side as well as the hardware management and monitoring on system side in detail. We further introduce eeMark, a benchmark for computational performance and energy efficiency which is especially tailored for HPC systems.