Distributed Java-based software systems are increasingly deployed onto heterogeneous mobile platforms with limited battery resources. In this domain, it is a crucial issue to preserve the energy resource and prolong the system?s lifetime. To address this problem, we first suggest a framework that allows the system engineer to estimate the energy consumption of a distributed Java-based software system both during system construction-time and during runtime. Based on our energy estimation framework, we then present two efficient approaches for reducing the software system?s energy consumption and consequently increasing the system?s lifetime. Finally, we discuss our strategy for evaluating our estimation framework and energy saving approaches.