Availability of renewable energy now makes solar energy the right choice because of its advantages and easy application compared to other renewable energy sources. Monitoring of the output parameters of solar power plants needs to be done to assess the performance and efficiency of a solar power plant in real environmental conditions. The aims of research is to provide a direct and real time monitoring. This research has been carried out in solar power plants at Engineering Physics Department, FTI-ITS. The design of an ATmega32 microcontroller-based system that is integrated with Raspberry-pi as a data acquisition system. Data reading solar power plants output parameters stored in memory can be downloaded at any time. The analysis result shows that the efficiency of photovoltaic arrays is 10.78 %. The total efficiency of the solar power plants system is 8.05 %.