Most wireless sensor nodes are battery operated since they are widely deployed and not easy to have a constant and stable power supply such as AC source. When a sensor node is running out of energy, it will lose of functionalities supposed, including physical quantity sensing and data forwarding for itself and other sensor nodes. This research aimed at a sensor node follows IEEE Std. 802.15.4-2015 time-slotted channel-hopping(TSCH) MAC. The target under-examined is a TI CC2538-based sensor node (board). A specific schedule and measurement were proposed to develop mathematical models of energy dissipation for transmission, receiving, enhanced-beacon (EB) and idle slots, respectively. With the experience, the power consumption of sensor nodes and their lifetime thus can be estimated handled well in practical use.