This study supports the effort of the Association of Southeast Asian Nations (ASEAN) to improve and harmonize AC energy-efficiency standards by adopting CSPF in accordance with International Organization for Standardization (ISO) Standard 16358. This report provides an overview of seasonal AC energy-efficiency metrics, assesses the regional climatic conditions in ASEAN countries, and makes recommendations for adopting ISO standard 16358 in a harmonized way across the region. It explores ASEAN-specific temperature profiles, the United for Efficiency (U4E) Model Regulation Guidelines’ temperature bin hours, as well as ISO 16358 temperature bin hours to evaluate the efficiency of ACs. The results show the superiority of CSPF over the traditional energy-efficiency ratio (EER) metric for capturing the higher seasonal efficiency of variable-speed ACs. The results also quantify the potential energy savings from the variable-speed ACs, which range from 25%–60% compared with the lowest-efficiency fixed-speed unit. This report also provides an overview of selected energy-efficiency standards and labeling policies for ACs internationally, including the U4E Model Regulation Guidelines for ACs and other countries in the Asia Pacific region such as China (expected revision in 2022), India, Japan, and Republic of Korea (South Korea). Finally, the report offers several recommendations for discussion amongst the ASEAN member states. The analyses demonstrated in this report for ASEAN can also be applied to considering adoption of seasonal AC energy-efficiency metrics for standards and labeling in other countries and regions.