Urban　building　retrofitting　is　a　critical　approach　for　energy　conservation　and　carbon　reduction,　and　proper　quantification　tools　could　help　lower　the　cost　for　large-scale　urban　renewal.　This　paper　introduces　City　Energy　Lab　(CityEL),　a　web-based　platform　that　supports　city-scale　building　energy　efficiency.　Compared　to　existing　Urban　Building　Energy　Modeling　(UBEM)　tools,　which　often　focus　on　aggregated　regional　results,　CityEL　not　only　facilitates　rapid　UBEM　but　also　focuses　on　analyzing　multiple　neighborhood　scales,　particularly　for　the　renovation　of　old　residential　neighborhoods.　CityEL　uses　AutoBPS　as　its　core　engine　to　establish　benchmark　and　energy　retrofit　models　and　utilizes　Geographic　Information　System　(GIS)　tools　to　enable　rapid　modeling,　multineighborhood　benchmarking,　and　comprehensive　retrofit　scenario　evaluation.　By　streamlining　energy　benchmarking,　retrofit　scenario　development,　and　economic　viability　analysis,　CityEL　provides　a　comprehensive　framework　for　scalable,　cost-effective　urban　renewal　decisions.　To　illustrate　its　capabilities,　CityEL　was　applied　in　a　case　study　of　Shanghai＇s　Huangpu　District,　where　the　platform　modelled　7934　buildings　across　304　neighborhoods,　245　neighborhoods　were　identified　as　economically　viable　for　retrofitting,　reducing　electricity　consumption　to　786.4　GWh　and　gas　consumption　to　303.2　GWh,　respectively.　These　findings　highlight　CityEL＇s　role　in　streamlining　multi-scale　decision-making　and　advancing　methodological　frameworks　for　sustainable　urban　energy　management.