The growing presence of concurrent heterogeneous wireless access networks, together with the increasing service demands from the end-users, require re-thinking of current access selection polices and appropriate management mechanisms, namely concerning QoS, energy efficiency, etc. The recent IEEE 802.21 standard introduces link layer intelligence as well as related network information to upper layers in order to optimise handovers between networks of different technologies, such as WiMAX, Wi-Fi and 3GPP. With the massification of mobile terminals with multiple wireless interfaces it is important to efficiently manage those interfaces not only to appropriately provide the requested services to the user, but also to do that in an energy efficient way in order to allow higher mobility to the user by extending the battery life of its terminal. In this article the IEEE 802.21 standard is briefly introduced, presented in the signalling in a handover between WiMAX and Wi-Fi, and exploited through an implementation in ns-2 introducing a simple, but effective, energy saving approach.