High data rate is a challenge for the next generation cellular networks. This objective needs a significant densification of relay nodes within macro cell. In the LTE-Advanced network, multi-hop relaying has been taken as a promising key technique to provide high throughput to the users and to improve the area coverage. Besides, minimizing the energy consumption and electromagnetic pollution is an economic challenge for the operators. This paper is focused on relay based heterogeneous cellular network like LTE-Advanced. We investigate the problem of throughput and energy consumption optimization. Our contributions are two-fold. First, we develop an optimization tool to calculate an optimal offline configuration of heterogeneous cellular network that maximizes the network capacity with low energy consumption. Second, we highlight a significant gain due to the deployment of relay nodes and we investigate the energy- capacity tradeoff.