The Electric Power Research Institute (EPRI) maintains an energy-economy model of the United States called the U.S. Regional Economy, Greenhouse Gas, and Energy (US-REGEN) Model. First developed in 2011, the model combines a detailed dispatch and capacity expansion model of the United States electric sector with an economy-wide end-use model disaggregated by sector and activity. This report describes the model, the methodology and theory that underlie it, and the construction of the associated datasets that inform the model. The original model documentation was completed in 2012 and underwent a review process by external experts and EPRI staff and members. The model is regularly updated, and features are added to address new research questions. In particular, an end-use energy demand model was developed during 2016-17 to improve the characterization of hourly electricity demand. This version of the documentation describes the model’s structure as of 2019.