Nowadays, power consumption at container terminals is related to flexible loads. Arguably, the most significant flexible loads, are the refrigerated containers, termed reefers. On average, reefers are responsible for 47.87% of the total energy consumption of container terminals. To control the reefers in a container terminal, it is hard to succeed with conventional methods. The Multi-agent systems (MAS) are well suited to control complex systems. In this paper, we show that MAS can be particularly well-suited to control reefers in a container terminal. A MAS system, implemented in JADE, is proposed for active power management of reefers. Additionally we use a fuzzy logic system, integrated in the MAS structure, to estimate the coefficient of utilization of the reefers. The results of our simulations with real data of a large terminal, proved the effectiveness of the method. A reduction of 37.08% to total energy cost of reefers at a container terminal was achieved.