We are moving from the Personal Computer (PC) age (i.e., one computing device per person ) to the Ubiquitous Computing age in which individual users utilize, at the same time, several electronic platforms through which they can access all the required information whenever and wherever they may be. Since the basic components of ad hoc wireless networks are mostly battery-operated portable devices, power conservation is one of the central issues of such networks. Power-conservative designs for ad hoc networks pose many challenges due to the lack of central coordination facilities.The purpose of this paper is to provide a comprehensive discussion of the power-optimization in mobile ad hoc networks based on routing.