— In sensor networks, MAC protocols based on Time Division Multiple Access (TDMA) with wakeup and sleep periods have attracted considerable interest because of their low power consumption and collision free operation. In this paper, we develop analytic models to evaluate the performance of such protocols. The model presented in this paper characterizes the queueing delays associated with the MAC layer as well as the energy consumed at MAC layer, by modeling the system as a queue with general service time distribution with both polling and vacations. The analysis is validated by comparison with simulation results using the NS-2 simulator. Our results show that polling based TDMA with sleep and wakeup cycles has lower delays and lower energy consumption as compared to SMAC.