Wireless sensor networks have been the object of many recent studies. They have applications in various domains such as building monitoring, habitat and environmental monitoring. The deployed sensors are able to gather information about sensed phenomena and route them towards a base station for later processing and decision making. The nodes are often deployed in unfriendly environments that are hard to access. Furthermore, sensors are subject to hard energy constraints. The usual goal of a wireless sensor network is to sense in a precise fashion a phenomenon for as long as possible. For all these reasons, the development of power aware routing algorithms i.e. algorithms which would permit an extended lifetime of the network is of capital importance.