Solar energy is one of the most environmentally friendly renewable energy sources and has significant potential to support energy transition while reducing carbon emissions. However, the performance of solar panels is strongly influenced by surface temperature, where an increase above 25 °C can reduce energy conversion efficiency by approximately 0.4–0.5% per °C. This condition is common in tropical regions such as Indonesia, thus requiring an effective cooling strategy to maintain optimal performance. This study aims to implement an Internet of Things (IoT)-based cooling system on solar panels and analyze its effectiveness in improving output power. The system was developed using an ESP32 microcontroller, a DS18B20 temperature sensor, and an INA219 sensor to measure voltage and current, along with actuators consisting of a DC water pump, DC fan, and Peltier module controlled automatically through a relay. Monitoring data were transmitted in real-time to the Blynk platform and Google Spreadsheet for
analysis. Experimental results showed that the cooling system successfully reduced the panel temperature by an average of 4–6 °C, lowering it from about 48 °C to 42–43 °C. As a result, the output power increased by 7–9 W, equivalent to around 11% compared to the condition without cooling. These findings demonstrate that the IoT-based cooling system is effective in enhancing solar panel efficiency, particularly in tropical climates with high solar radiation.