Smart Building Energy is the application of IoT sensors, cloud analytics, and automated controls to optimize how buildings consume energy. It includes real-time monitoring of HVAC systems, intelligent lighting that responds to occupancy and daylight, demand response programs, and predictive maintenance that prevents equipment failures. Modern smart buildings collect continuous data on temperature, humidity, air quality, occupancy, and energy usage, then use machine learning to predict demand, identify inefficiencies, and automatically adjust systems to minimize waste while maintaining comfort.