The U.S. Energy Services Company (ESCO) industry is often cited as the most successful model for the private sector delivery of energy-efficiency services. This study documents actual performance of the ESCO industry in order to provide policymakers and investors with objective information and customers with a resource for benchmarking proposed projects relative to industry performance. We have assembled a database of nearly 1500 case studies of energy efficiency projects – the most comprehensive data set of the U.S. ESCO industry available. These projects include $2.55B of work completed by 51 ESCOs and span much of the history of this industry. We estimate that the ESCO industry completed $1.8-2.1B of projects in 2000. The industry has grown rapidly over the last decade with revenues increasing at a 24% annualized rate. We summarize and compare project characteristics and costs and analyze energy savings, including the relationship between predicted and actual savings. ESCOs typically invested about $2.30/ft per project in various energy efficiency improvements, although there is large variation in project costs within and across market segments. We find that lighting-only projects report median electricity savings of 47% of targeted equipment consumption; the median for lighting-&-nonlighting projects is 23% of the total electric bill baseline. We examine project economics, including project net benefits, benefit/cost ratio and simple payback time. Median simple payback time is seven years for institutional sector projects and three years in the private sector. We estimate direct economic benefits of $1.62 billion for the 1080 projects in our database with both cost and savings data. The median benefit/cost ratio is 2.1 for 309 private sector projects and 1.6 for 771 institutional sector projects. We discuss the role of policies and programs adopted by state/federal legislatures and agencies that have played an important role in stimulating ESCO activity in various markets. Finally, we estimate the overall size and growth of the energy-efficiency services industry over the last ten years based on a survey of 63 ESCOs.