This report describes the work of EPA and the automobile manufacturing industry to develop an Energy Performance Indicator (EPI) for assembly plants. These types of plants are defined as those that produce passenger cars, light-duty trucks, sport utility vehicles, and vans in the United States. Learn how EPA uses EPIs to encourage industries to voluntarily improve their energy use. The report describes the data and statistical methods used to construct the EPI for automobile assembly plants. The equations are presented with instructions for using them in an associated Excel spreadsheet.