Network services are diversified, and each service requires different quality of service (QoS). This paper proposes a QoS-aware sleep controller for energy-efficient optical network units (ONUs), which are installed at customer premises. The proposed controller reduces the power consumption of ONUs, while maintaining the QoS for downstream traffic at a constant level. Introducing a feedback control technique to the controller improves the QoS compared with conventional controllers. Simulation results confirm the proposed controller provides better performance than a conventional controller in terms of power consumption and average queuing delay.