The Internet-of-Things applications use embedded processors to execute lightweight tasks for sensing and management of communications. These applications use different energy harvesting strategies such as clock gating and domain switching. However, some power supplies for sensor systems are designed for low-power delivery rather than low-energy battery consumption. Regarding power consumption, it is important to choose the system-based processor in which some variables are taken into account. Depending on the final IoT application, such variables are power consumption, area, performance, and software tools. This paper presents an 8bits and 32bits based System on Chip (SoC) in a General Purpose (GP) CMOS technology. The two processors are implemented in the same tape-out and the same peripherals. The experiment results show a 1.69µW and 1.76µW in the 32bits and 8bits SoC, respectively. In terms of area, the 32bits processor is 46% overhead of the 8bits processor, with 6.6-kGE over 3.6-kGE. Finally, the 32bits SoC presents a 1.11 DMIPS and 8bits SoC a 1.38 DMIPS.