BVTs can be dynamically reconfigured to accomplish a specific capacity-reach tradeoff. Together with flexible grid reconfigurable optical add drop multiplexers (Roadms), they provide a great deal of flexibility on the assignment of physical resources, which can be leveraged for energy saving purposes. Analysis in terms of energy efficiency in different network scenarios and conditions (i.e. different-sized network topologies, static and dynamic traffic operations, unprotected and protected networks, and different traffic loads) showed significant improvements with respect to the conventional WDM networks. these advantages mainly come fro the possibility of providing dynamic resource adaptation to the actual load , but EON also has better spectra efficiency with respect to conventional WDM networks, which can be further translated to reduced energy consumption