In this paper, a hybrid channel access mechanism is proposed for the wireless sensor network that considers the channel access procedure of IEEE 802.15.4 and combines the binary exponential backoff mechanism of IEEE 802.11 due to packet collision of nodes after successful channel assessment. Taking the backlogged nodes due to collision, an extended linear feedback model is developed and a discrete-time Markov chain model is designed to analyze the successful and failure probabilities of the system model of the wireless sensor network. Besides, an energy consumption model for the one hop wireless sensor network is developed based on our models and hybrid channel access mechanism. Extensive performance analysis are done to study the effect of binary exponential contention window on energy consumption of the nodes and it is verified that our simulation results totally match with the theoretical results for different size of contention windows and node numbers.