Abstract: Since, the demand for an autonomous systems such as Wireless Sensor Network (WSN) nodes or Internet of Thing (IoT) devices is growing these days and due to the fact the periodic maintenance and battery replacement for such systems may not be an economical solution, therefore battery substitution with an energy harvesting system is crucial. The direct output current of the Thermo Electric Harvester (TEH) has made it a popular potential of electrical energy source to substitute battery, however the energy that’s generated by TEH needs to match the minimum electrical power requires to operate the electronic system. The focus of this research paper is to investigate the power consumption of a wireless sensor node which is powered by TEH. The wireless node in this project contains a MEGA328P Micro Controller Unit (MCU), a wireless transceiver nRF24L01, DHT22 sensor and a thermal energy harvester with a power conditioning circuit. The system is equipped with an energy aware algorithm to reduce the power consumption. This algorithm lets the node sleep for 10 sec and then wake it up for a few millisec to read and send a data. The experimental results show that the system required 46 mW in sleep mode while it consumes about 53.5 mW during active mode. The operational performance of the system is evaluated using 7.4 V rechargeable Lipo battery and compared with TEH in term of operational longevity. The results show that the Lipo battery able to operate the system continuously for 33 h whereas the TEH has successfully kept the system running as long as there is a heat source with a gradient of 40°C.