Along with the widespread usage of mobile devices supporting multiple radio interfaces, users can connect to the mobile operator's network using different access technologies such as UMTS, WLAN and WiMAX/LTE. Depending on the network conditions and the QoS requirements of users, the usage of the right technology at the right time can provide more effective networking with higher data rate, lower cost, longer battery duration, and higher coverage area. To enable this networking effectiveness, a seamless handover mechanism to minimize service disruption is required. IEEE 802.21, which defines a set of standards for media independent handover, is capable of realizing both horizontal and vertical handovers. In this paper, a new algorithm is proposed to provide energy efficient handovers among UMTS, WiMAX, and WLAN networks. The proposed algorithm is implemented within the IEEE 802.21 framework and its performance analysis is performed using the ns-2.29 simulator. Simulation results show that the proposed algorithm significantly increases the service duration and hence decreases packet losses by dynamically changing the video downloading rate according to handover decisions and the remaining battery power levels.