Dynamic reconfiguration of FPGA in the networking hardware device is a feature which can be exploited in numerous networking applications. By reconfiguration we can change either the functionality, performance or even energy consumption of an area on the FPGA. This property can be exploited in a number of ways, in different application areas. However, the question of performance and power consumption trade-off in these situations is still an open issue. In this paper we address this issue by investigating different use cases and introducing a general approach of algorithmic optimization of power consumption based on dynamic reconfiguration. Our findings are supported by extensive SystemC/TLM hardware level simulations.