Monitoring-based commissioning (MBCx) is a program approach that combines permanent building-energy-system monitoring with standard retrocommissioning practices to provide substantial, persistent energy savings. It’s based on the ability of permanent monitoring systems to increase the effectiveness of retrocommissioning by providing a means to verify and ensure the persistence of savings achieved through operational improvements. Additionally, permanent monitoring systems can identify previously unrecognizable and unquantifiable savings opportunities—such as equipment cycling; excessive simultaneous heating and cooling; or the unintended nighttime operation of air handlers, chillers, boilers, or lighting equipment—that would not be apparent from monthly utility readings. A pilot program has demonstrated MBCx's ability to reduce total energy consumption in commercial buildings by a median value of 10 percent in a portfolio with minimal project screening.