The paper presents system level simulation results on future base station energy saving using a time-triggered sleep model. The energy efficiency of future base station is compared in macro cellular network against a comparable baseline without usage of sleep modes. Furthermore, results for corresponding 4G case are shown using a restricted set of sleep modes supported by 4G networks. The paper also proposes an analytical method for approximating system level energy saving gains of a base station. The results show rising trend of energy saving gain, when increasing the SS burst period of a 5G base station. However, the gains are seen to saturate at certain SS burst periodicity of 20 ms–40 ms. Furthermore, the results illustrate the rising energy saving gains towards reduced system load. The results for 4G show energy saving gains up to 22 % due to reduced set of sleep modes available for use. Finally, the calculated energy saving gain values are closely aligned with the simulated values.