In this paper, we study joint topology management and energy cooperation in cellular networks. The topology management scheme transfers users (traffic) from one base station (BS) to another BS by adjusting the cell-size of the BSs, and the energy cooperation scheme transfers harvested energy from one BS to another BS. We first formulate a joint topology management and energy cooperation problem which aims at minimizing the total on-grid energy consumption while satisfying the quality-of-service (QoS) requirement of each user. Then, by solving the problem, we develop a joint topology management and energy cooperation scheme. Topology management and energy cooperation are different approaches to save the on-grid energy consumption, and each scheme is effective to save the on-grid energy consumption in different environments such as different traffic and weather conditions. Through the simulation results, we show which scheme is more effective to save the on-grid energy consumption considering various environments. In addition, we also show that our joint scheme is most effective to deal with the environment which changes dynamically.