In this work we study energy efficient routing strategies for wireless ad-hoc networks. In this kind of networks, energy is a scarce resource and its conservation and efficient use is a major issue. Our strategy follows the multi-cost routing approach, according to which a cost vector of various parameters is assigned to each link. The parameters of interest are the number of hops on a path, and the residual energy and the transmission power of the nodes on the path. These parameters are combined in various optimization functions, corresponding to different routing algorithms, for selecting the optimal path. We evaluate the routing algorithms proposed in a number of scenarios, with respect to energy consumption, throughput and other performance parameters of interest. From the experiments conducted we conclude that routing algorithms that take into account energy related parameters, increase the lifetime of the network, while achieving better performance than other approaches, such as minimum hop routing.