A model-based real-time whole building energy monitoring and diagnostics is presented. The proposed system continuously acquires performance measurements of HVAC, lighting and plug load usage from the Building Energy Management System (BEMS) and compares these measurements in real-time to a calibrated reference EnergyPlus model. The structure of categories for extracted data and model outputs is described, along with discussion of adjustments necessary to EnergyPlus reporting and set up of BEMS trending. A proof of concept demonstration is presented.