The need to manage the energy consumption of network infrastructure has been addressed by a significant body of work in recent years. In general, energy management capabilities were developed independently and optimized for particular network layers and node features. The interaction between multiple such green capabilities when deployed simultaneously, as well as potential interactions with other existing functionality such as quality of service functions, need to be managed transparently by the operators. We developed SLIM, the SustainabiLity Information Model for Energy Efficiency Policies, as an addon to the IETF Policy Core Information Model Extension to allow unifying the management of green capabilities throughout the network. We illustrate the flexibility of our approach by presenting a use case and describing an energy management system where SLIM was used.