Determining　the　real　energy　consumption　and　usage　pattern　of　a　room　air-conditioner　(RAC)　are　important　issues　from　the　point　of　view　of　both　RAC　design　and　evaluation　of　its　energy　efficiency.　An　air　conditioner＇s　running　time　is　fundamental　data　for　the　calculation　of　SEER　and　APF　values.　Therefore,　in　2010,　a　nationwide　investigation　of　RAC　usage　was　conducted　and　400　selected　air-conditioning-units　were　monitored　for　a　full　year　to　obtain　data　on　their　cooling　and　heating　usage.　Two　running　time　curves　(cooling　and　heating)　were　obtained　for　the　air-conditioners　as　a　function　of　outdoor　air　temperatures　using　statistical　analysis.　The　results　show　that　the　27-30　degrees　C　temperature　range　accounts　for　more　than　52%　of　the　cooling　time.　Conversely,　the　0-8　degrees　C　temperature　range　is　associated　with　more　than　75%　of　the　heating　time.　The　research　presented　in　this　paper　has　significantly　contributed　to　China＇s　new　variable-speed　RAC　efficiency　standard　(GB21455-2013).　It　also　has　far-reaching　implications　for　both　the　air-conditioner　industry　and　energy　policy　in　China　due　to　its　different　method　of　calculating　energy　efficiency.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.