Reasonably accurate reference power consumption values are required for any work that evaluates power consumption in telecommunication networks. Many existing works provide or use optimal power rating (W/Gbps) values, i.e. the power rating achieved for the maximum capacity of the system, with the shared relative overhead thus being the smallest. In this paper, we evaluate how power rating values are influenced by practical equipment filling levels for core IP-over-WDM equipment. We show that, over the equipment's lifetime, for IP/MPLS routers it is reasonable to almost double the optimal power rating value under real-life equipment filling conditions. For Optical Line Amplifiers a correction factor of 1.5 is appropriate, and for WDM terminals the required correction is almost negligible, i.e. 1.1. Furthermore, power measurements on IP routers and Optical Line Amplifiers show that their power consumption marginally depends on traffic load.