Building energy modeling is currently an expensive, manual roadblock to optimizing indoor climate systems and achieving critical decarbonization goals. Power Twin offers an innovative solution for building owners, energy auditors, and planners. Using advanced 3D surveying and intelligent algorithms, we automatically generate a high-fidelity Building Information Model that represents its geometry, systems and physical properties. From this BIM, we derive a Digital Twin: a simulation-ready, dynamic model used for accurate energy simulations. This process allows stakeholders to simulate and evaluate system evolutions, such as adding insulation or changing heating sources, before capital is invested, reducing costs and improving sustainability.