Billions of low-power wireless sensors will be deployed as the Internet of Things (IoT) evolves and connected online objects become integrated with daily lives. Using batteries to power up wireless sensors will be a formidable challenge. In this work, a new 250 nW low power energy harvesting solution for IoT sensors is presented in which the available sensor’s microcontroller is reused to control the energy harvesting process. A new boost converter circuit is proposed and implemented where the number of components and power consumption of the control unit is much lower compared to similar energy harvesting solutions. A commercially available smart sensor is used to validate the proposed solution. Experimental measurements show that the implemented boost converter consumes about 250 nW with 95% efficiency at 8 μW power output and the sensor can properly operate with a low light intensity of 200 Lux which is available in most indoor environments.