ALLIANCES is a newly proposed wireless MAC protocol that exploits the cooperation of source nodes and relay nodes to resolve collisions and further improve throughput. Until now, ALLIANCES did not consider energy, which is the most precious commodity of mobile communications. In this paper, we propose an energy-conserving version of ALLIANCES that introduces a sleep state. Our analytical results show that the energy-conserving model can save at least 54% of energy consumption when compared to the original energy model (referred to as the basic energy model in this paper). Because a relay selection scheme is a significant piece of ALLIANCES, directly affecting the throughput and the energy distribution, we also propose an energy-aware relay selection scheme (ERS). ERS maintains the performance benefits of the previously proposed location relay selection scheme (LRS), but more evenly distributes the amount of energy remaining throughout the network. We implement our energy-conserving model and ERS in the popular network simulator (NS-2) to evaluate and compare the energy remaining at each node and the network's throughput when using LRS and ERS. Simulation results show that the energy-conserving model can save up to 80% of energy without nodes taking longer to communicate. In addition, using the energy-conserving model, ERS provides 23.3% longer lifetime of the network than LRS, without noticeable throughput degradation.