In cognitive radio networks (CRNs), primary-user (PUs) localization is a key aspect for improving network performance in terms of reliability and power adaptation. However, energy efficiency becomes a critical issue for localization in CRNs due to the limited energy storage in CR devices. In this paper, we propose an energy-efficient cooperative localization algorithm (EE-CLA) for PU positioning using a mobile-aided CR. Since cooperative communication among CRs is energy demanding, a mobile CR manager is introduced to balance the requirements for positional accuracy and power consumption restrictions by waking up only an appropriate number of CRs collaborating with the mobile CR manager. To investigate the influence of accurate location information, a location-aware CR (LaCR) routing protocol is also applied. Simulations are conducted to evaluate the performance of both the proposed EE-CLA and the LaCR protocol. Results confirm that the proposed EE-CLA outperforms its simplified version, which is named the CLA, in terms of energy efficiency. Moreover, significant gains are obtained with the LaCR protocol in terms of CR end-to-end performance and PU collision risk by using the localization information obtained from the EE-CLA.