Eliot Crowe analyzes the costs and savings of building commissioning (Cx) in North America between 1984 and 2018. The authors collected data from more than 1,500 buildings to examine how the effectiveness of Cx, for both new construction and existing buildings, has evolved over time. The report examines different types of Cx projects, including utility-sponsored energy-saving projects, monitoring-based commissioning (MBCx), and non-utility-funded Cx projects. The study concludes that Cx remains an effective method of saving energy and that Cx costs have declined since 2009, while the size and complexity of projects have increased.