Solar Power Plants (PLTS) are a renewable energy solution whose use continues to grow. However, solar panels installed in open spaces are very susceptible to exposure to
pollutants which can block light absorption and reduce their effectiveness. This research aims to analyze the influence of pollutants on the relative efficiency of solar panel power and evaluate the performance of an Internet of Things (IoT) based monitoring system. The research method was carried out through field experiments using an ESP32
microcontroller, INA219 sensor, step-down Mini560 module, as well as the Blynk and Google Spreadsheet platforms for real-time monitoring. The research results show that in clean conditions, solar panels produce an average power of 11.87 W with irradiation of 526.57 W/m² with a relative efficiency of 100%. Under conditions of 3 grams of combustion dust, the average power decreased to 9.14 W with irradiation of 510.52 W/m² and efficiency of 77%. Meanwhile, three-point wet pollutant reduces the average power to 8.04 W at irradiation of 500.52 W/m² with an efficiency of 67.73%. The most significant reduction occurred in 5 gram carbon soot with an average power of only 5.26 W at irradiation of 472.63 W/m² and efficiency of 44.31%. This finding proves that the lower the irradiation received due to pollutants, the lower the solar panel output power. Dry pollutants, especially carbon soot, have the most detrimental impact compared to wet pollutants. The IoT system has proven to be effective in recording data in real-time, so that it can support monitoring and optimizing PLTS operations.