Electrochromic　(EC)　windows　can　prevent　glare　by　adjusting　their　tinting　state,　but　the　tinted　EC　glass　will　affect　the　use　of　daylight　in　the　room,　resulting　in　the　increase　of　lighting　energy　consumption.　Splitting　the　EC　window　into　several　panes　and　tinting　only　a　portion　of　them　can　effectively　mitigate　the　conflict　between　glare　prevention　and　the　usage　of　daylight.　However,　there　is　a　lack　of　design　methods　for　EC　window　split　pane　configurations　to　realize　further　lighting　energy-saving　potential.　To　address　this　problem,　this　study　proposed　an　optimal　design　method　for　EC　window　split　pane　configuration.　This　method　is　based　on　the　glare　calculation　model　and　aims　to　obtain　the　minimum　tinted　area　hours　(TAH)　of　the　EC　window.　Taking　a　south-facing　EC　window　office　building　in　Beijing　as　a　case　study,　the　effectiveness　of　the　proposed　design　method　was　investigated　by　simulation.　Results　show　the　proposed　design　method　identified　the　most　energy-efficient　and　comfortable　split　panes　scheme.　By　combining　with　the　split-pane　glare　control　method,　95.3%　of　intolerable　glare　was　prevented,　and　a　useful　daylight　illumination　index　of　73.3%　was　achieved.　It　also　significantly　improved　building　energy　efficiency,　saving　29.8%　of　lighting　energy　consumption　compared　to　whole　window　design　scheme.　This　study　provides　a　promising　design　methodology　for　the　high-performance　application　of　EC　windows　in　buildings.　©　2023　Elsevier　Ltd