The emergence of the Internet of Things has caused the proliferation of wireless sensor networks (WSNs) used to capture and distribute all kind of data. These WSNs need to be completely autonomous in order to be easily deployable and therefore the use of renewable energies such as sunlight is often the only option available to supply these systems. There are currently a variety of applications supplied with small photovoltaic (PV) systems. In order to increase the efficiency of these PV systems, Maximum Power Point Trackers (MPPTs) are used. These electronic circuits are capable of harvesting the maximum power available at the PV modules with changing environmental conditions. The MPPT algorithm was usually programmed using microcontrollers but lately few low-cost commercial MPPTs for low power applications have appeared in the marketplace. This project has been carried out with the objective of developing a complete solar energy harvesting solution for wireless routers used in Wireless Sensor Networks (WSNs). The solution includes the PV modules, the MPPT or power controller and the battery, and it has been designed to be integrated into the housing of a commercial WSN router.