Energy constraint is a key feature inwireless sensor networks (WSNs),where sensor nodes are battery powered. In this context, maintenance efforts are frequently required to maintain the lifetime and load balance of the network. In some scenarios, like disaster prevention and chemical process control, changing or recharging nodes batteries is difficult and expensive. This creates an increasing need to develop alternative energy-efficient solutions to power nodes and reduce the energy consumption during network performance. Energy-aware techniques are essential to maintain the sustainability and performance of the network, while reducing the cost as well as the energy consumption. In this chapter, energy dissipation sources are studied to explore new solutions to conserve energy in the network. Also, a detailed description of available energy conservation and optimization techniques for WSNs is presented.