Research Panaran Gas Engine Power Plant (PLTMG) Batam uses a radiator cooling system to keep the engine temperature stable. However, the existing water cooling spray system is still manual, so the booster pump is often operated continuously without considering the actual temperature of the radiator. This leads to waste of energy, high operational costs, and shortens the life of the equipment. This research designs and implements an Internet of Things (IoT)-based water cooler system using an ESP32 microcontroller, max6675 temperature sensor and blynk application as monitoring and control media. This system allows the pump to work automatically based on the radiator temperature, while at the same time can be controlled and monitored via smartphone in real-time. The test results show that the IoT system is able to reduce operational time by 23% compared to the previous method which must be turned on continuously. Thus providing operational energy efficiency of 18.7% from existing conditions. The temperature of the radiator is successfully monitored with the sensor accuracy level reaching ±1.5°C. Thus, the application of IoT to the water cooler system is proven to be able to increase energy efficiency, extend pump life, and facilitate operators in monitoring and control remotely