Electricity　demand　for　room　air　conditioners　(ACs)　has　been　growing　significantly　in　China　in　response　to　rapid　economic　development　and　mounting　impacts　of　climate　change.　In　this　study,　we　use　the　bottom-up　model　approach　to　predict　the　penetration　rate　of　room　ACs　in　the　residential　building　sector　of　China　at　the　provincial　level,　with　the　consideration　of　the　urban-rural　heterogeneity.　In　addition,　we　assess　co-benefits　associated　with　enhanced　energy　efficiency　improvement　of　AC　systems　and　the　adoption　of　low-global-warming-potential　(low-GWP)　refrigerants　in　AC　systems.　The　results　indicate　that　the　stock　of　room　ACs　in　China　grows　from　568　million　units　in　2015　to　997　million　units　in　2030　and　1.1　billion　units　in　2050.　The　annual　electricity　saving　from　switching　to　more　efficient　ACs　using　low-GWP　refrigerants　is　estimated　at　almost　1000　TWh　in　2050　when　taking　account　of　the　full　technical　energy　efficiency　potential.　This　is　equivalent　to　approximately　4%　of　the　expected　total　energy　consumption　in　the　Chinese　building　sector　in　2050　or　the　avoidance　of　284　new　coal-fired　power　plants　of　500　MW　each.　The　cumulative　CO2eq　mitigation　associated　with　both　the　electricity　savings　and　the　substitution　of　high-GWP　refrigerants　makes　up　2.6%　of　total　business-as-usual　CO2eq　emissions　in　China　over　the　period　2020　to　2050.　The　transition　toward　the　uptake　of　low-GWP　refrigerants　is　as　vital　as　the　energy　efficiency　improvement　of　new　room　ACs,　which　can　help　and　accelerate　the　ultimate　goal　of　building　a　low-carbon　society　in　China.