This work proposes an energy-efficient duty-cyclebased hybrid medium access control protocol. The proposed protocol optimally adjusts the turn-on and off time of the trans-receiver radio to save energy consumption. Both cluster head and sensing devices save energy by estimating the utilization of slots. In reserved slot duration, each sensor device checks its buffer status in a regular interval and turns off its radio when the buffer becomes empty. Each sensor device transmits a slot utilization status to the cluster head device. Cluster head device also turn-on and off its radio based on slot utilization status of sensing devices. A duty cycle approach is proposed for optimal energy consumption. The proposed protocol uses less energy than existing equivalent protocols, according to the mathematical and simulation results. For simulation study, the network is analysed for low, medium, and high data traffic conditions. Simulation results depict, exactly similar results of analytical and mathematical analysis prove the validity of the work.