A flexible Wireless Sensor Network platform for easier implementation of diverse applications has been developed and deployed at one of the Institute Superior Tecnico - Technical University of Lisbon (IST-TUL) campus. Since its initial deployment in 2007, this test-bed has grown steadily, supporting new nodes, applications and experiments. However, some initial problems, which were solved on an ad hoc basis, are becoming more serious as the network spans throughout the campus. Major issues, like global power management, have to be tackled not only with traditional protocol level approaches but also from a system’s viewpoint, providing solutions that are capable of guaranteeing a consistent operational test-bed. We discuss the main issues related with the development of power management solutions, at different levels, presenting our architecture, design choices and implementation. We also address the lessons learnt from its integration in the platform. Results of the experimental evaluation of our solution have shown considerable energy savings (extending the network lifetime up to 9 times) even in the presence of demanding applications.