This document proposes a novel host selection algorithm called Energy-Efficient Particle Swarm Optimization (EE-PSO) for dynamic container consolidation in cloud data centers. The goal of the algorithm is to reduce energy consumption while maintaining quality of service levels. It was tested using the ContainerCloudSim toolkit on real-world workloads and was found to outperform existing algorithms in terms of energy savings, quality of service guarantees, number of new virtual machines created, and number of container migrations.