The rapid growth of mobile and wireless data services has spurred the requirement of the future 5G network for a very high throughput efficiency. In this paper, we investigate throughput maximization via optimized energy allocation and Automatic Repeat reQuest (ARQ) retransmission protocol. Using default energy allocation showed an inefficiency in average consumed energy throughout all retransmission attempts carried out to succeed an error-free packet reception. To overcome this limitation, we here suggest a judicious allotment of the available energy budget along transmission attempts (first transmission and potential retransmission) while keeping the total energy cost steady for each transmitted packet. For a given Signal to Noise Ratio (SNR), the optimal distribution of total available energy along all transmission attempts is determined through a Genetic Algorithm based search that exploits the throughput efficiency as a fitness function. Numerical results demonstrate the efficiency of the proposed strategy in terms of maximizing the average throughput efficiency and accordingly reveal the improvement in reducing the probability of packet erasure as well as the number of required transmissions to achieve high throughput.