Poor monitoring of a photovoltaic (PV) system is responsible for undetected faults that reduce the energy produced by the system and in the long run, decrease its lifespan. However, this challenge can be overcome by live monitoring of the electrical and environmental parameters of the PV system. Several wireless real-time monitoring systems are available, but none have a backup storage device and can only monitor a few parameters at a relatively high cost. Besides, these systems cannot monitor the battery storage and the inverter output. In this paper, we report a robust monitoring system developed for both local and remote live monitoring of a PV system. The electrical and environmental parameters of the PV system were monitored and saved using wireless sensor networks and Internet of Things (IoT) technology. This was achieved using two Atmega 328P microcontrollers, which formed the data acquisition units, and an ESP32 microcontroller for the master terminal unit. The data acquisition unit consists of two nodes: the PV node, and the battery node. All data are received by the master terminal unit and sent to the ThingSpeak online server using the IoT capability of the ESP32 microcontroller. The developed system was installed in a 12 V, 200 W standalone PV system, and all desired parameters were successfully monitored, logged, and transmitted to the cloud in real-time for easy accessibility by the users via the internet.