Energy reduction is critical to increase the mobility and to extend the mission period in the development of today?s pervasive computing systems. On the other hand, however, energy reduction must be subject to the requirements not to compromise the quality of service (QoS) that these systems need to provide. While most of the current research in energy-aware real-time scheduling has been focused on hard real-time systems, a large number of practical applications and systems exhibit more soft real-time nature. In this paper, we study the problem of minimizing energy for soft real-time systems with the requirements of QoS-guarantee. The QoS requirements are deterministically quantified with the (m,k)-constraints, which require that at least m out of any k consecutive jobs of a task meet their deadlines. To deal with the dynamic characteristics of such applications and systems, we propose a hybrid static/dynamic scheduling approach that can efficiently reduce the energy consumption while guaranteeing the (m,k)-constraints. The experimental results demonstrate that our proposed techniques outperform previous research significantly in terms of both the energy savings and QoS that can be achieved.