There are several approaches to reduce the energy consumption. Among them, one approach which allows for reducing the transmission energy consumption is Delay Tolerant Networks (DTNs). Several techniques are adopted to optimize the energy efficiency. Adjusting the resource allocation and decreasing the equipment usages are the basic two categories, which are used to reduce the energy consumption. With the increasing data transmission rate the energy consumption increases, which result in the diminishing of its efficiency. So, it is a necessity to manage the trade-off between energy and performance in Delay Tolerant Networks. The DTN nodes commonly operate on low-power battery resource; hence, there is need of improving the energy efficiency by using appropriate technique to increase the lifetime of the node and also to increase the probability of delivering the bundle. For that purpose, this paper describes the various techniques to achieve energy efficiency in Delay Tolerant Networks. © Springer Nature Singapore Pte Ltd. 2017.