Improving　the　energy　performance　of　windows　is　crucial　for　enhancing　the　overall　energy　conservation　of　buildings.　To　select　the　optimal　energy-efficient　windows　across　diverse　climate　conditions,　this　study　collected　3,597　windows　from　China,　then　classified　their　component　characteristics　and　thermophysical　properties.　According　to　the　survey,　the　dominant　window　type　in　China　is　casement　window　with　aluminum　(ALU)　frame　material,　which　accounts　for　71.17%　of　the　sample;　in　terms　of　glass　layers,　the　most　prevalent　are　double-layer　(DG)　(58.72%)　and　triple-layer　(TG)　(40.67%);　for　surface　coating,　the　majority　is　the　single-layer　coating　(SCO)　(65.22%),　followed　by　non-coating　(NCO)　(29.89%).　Afterwards,　respective　linear　regressions　between　thermophysical　parameters　(heat　transfer　coefficient　(U-value),　solar　heat　gain　coefficient　(g-value),　and　air　leakage　(AL))　and　component　factors　were　performed.　Furthermore,　an　energy　index　(EI)　model　of　windows　was　developed　to　evaluate　component　factors.　Five　distinct　climate　zones　of　China　and　four　orientations　were　investigated　to　explore　the　primary　window　components　influencing　energy　performance.　In　terms　of　the　south-facing　window,　the　dominant　factor　for　severe　cold　(SC)　and　temperate　(T)　zones　is　uniformly　the　glass　layer,　while　for　hot　summer　and　warm　winter　zone　(HSWW)　zone,　it　is　the　Low-E　coating　layer.　Additionally,　in　the　cold　(C)　and　hot　summer　and　cold　winter　(HSCW)　zones,　the　other　cardinal　directions　highlight　different　primary　components.　This　study　recommends　the　optimal　selection　of　window　component　factors　in　different　orientations　and　climates.　©　2023　Elsevier　B.V.