GSA’s Green Proving Ground is evaluating the energy efficiency potential of various technologies including variable refrigerant flow (VRF) HVAC systems. VRF systems are a mature technology with a large market share outside the U.S. with growing interest in the U.S. This report demonstrates the potential energy savings, cost effectiveness of the technology and impact on GSA’s buildings, as well as the broader market, while acknowledging some uncertainties about the energy performance.