We develop a novel traffic scheduling algorithm based on a master-slave linecard (LC) configuration to improve the energy-efficiency of hybrid fiber-coaxial (HFC) networks. The algorithm forwards packets to the master or slave LC adaptively according to the traffic load, and toggles the LCs between working and sleeping modes for energy-saving. To optimize the algorithm's key parameters, we model the system using a twodimensional Markov process and derive the analytical expressions of several performance metrics, including average packet delay, LC switching frequency, and energy efficiency improvement. We then verify the theoretical analysis with numerical simulations using the Monte Carlo method. Both the theoretical and simulation results indicate that the proposed algorithm can achieve significant energy efficiency improvement, while keeping the average packet delay and LC switching frequency low.