The rapid increase in global greenhouse gas emissions (GHG) has increased the demand for clean and efficient energy solutions for residential buildings. This paper presents a low-cost, real-time and modular Internet of Things (IoT) based smart energy management and monitoring system designed to optimise residential photovoltaic (PV) energy use. The system uses an ESP32 microcontroller with robust processing capability, built-in Wi-Fi and cost-effectiveness compared to Arduino and STM32 platforms. The INA219 monitors the PV system voltage and current. A DHT11 environmental sensor monitors environmental data in real time. Data is transmitted using the MQTT protocol with a lightweight, low-latency architecture suitable for IoT applications. The Grafana cloud provides visualisation and analysis. One of the system’s key features is the decision-making algorithm that continuously assesses the home’s energy needs throughout the day. When solar power generation exceeds demand, excess energy is smartly stored to the battery storage system, improving energy efficiency and reducing energy consumption.