Mobile air conditioning (MAC) systems are a significant source of greenhouse gas (GHG) emissions from vehicles. This study, conducted by the ICCT in partnership with the Institute for Governance & Sustainable Development (IGSD), examines the GHG benefits and costs of switching to improved refrigerants and more efficient AC systems. This research is intended to support implementation of the Kigali Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer, which requires the phase-down of HFC refrigerants and also targets improvements in energy efficiency.