Cognitive Radio Networks (CRNs) represent a cutting-edge solution to the growing problem of limited available spectrum. With the increasing demand for wireless communication services, the efficient utilization of spectrum resources becomes paramount. Green CRNs offer a dynamic and opportunistic approach by intelligently sensing and accessing idle licensed spectrum, known as white spaces focusing on environmentally conscious communication methods. These unoccupied frequency bands, left unused by primary users (PUs), present an opportunity for CRNs to enhance spectrum utilization and alleviate the spectrum scarcity challenge. In the presented study, we concentrate on energy conservation in “Green” CRNs, with a specific focus on base stations (BSs). We suggest an energy-efficient approach that utilizes multiple sleep modes employing an N-policy, with the objective of addressing the growing need for environmentally friendly communication practices. To model the energy-saving process and assess system performance, we employ a semi-Markov process (SMP). Moreover, the paper provides a detailed analysis of performance metrics, encompassing average latency for Secondary Users (SUs), throughput of the system, energy saving factor, and energy consumption.