Optimizing energy consumption has become a major concern in designing economical clusters. Scheduling precedence-constrained parallel tasks on clusters is challenging because of high communication overhead. Although duplication-based strategies are applied to minimize communication overhead, most of them merely consider schedule lengths, completely ignoring energy consumption of clusters. In this regard, we propose two energy-aware duplication scheduling algorithms, called EADUS and TEBUS, to schedule precedence-constrained parallel tasks. Unlike existing duplication-based scheduling algorithms that replicate all possible predecessors of each task, the proposed algorithms judiciously replicate predecessors only if the duplication can help in conserving energy. Our energy-aware scheduling strategies are conducive to balancing the scheduling length and energy consumption of precedence-constrained parallel tasks. Extensive experimental results based on real-world applications demonstrate...