Open-access electricity demand data are essential for meteorology–energy and climate–energy research, forecasting, and resilience planning. Yet in South and Southeast Asia (SASEA), such records are fragmented across sources, reported in inconsistent formats, and often difficult to find or access. This is a serious limitation in a region where electricity use and system stress are sensitive to monsoon variability, humid and dry heat, and other natural hazards.</p> <p>In this paper, we present and describe a harmonised electricity demand dataset for twelve SASEA countries (Bangladesh, Bhutan, India, Malaysia, Myanmar, Nepal, Oman, Philippines, Singapore, Sri Lanka, Taiwan, and Thailand) at daily national resolution, spanning 2013–2025 with country-dependent coverage. We compiled raw data from national utilities, regulators, and international providers using reproducible retrieval workflows (e.g., APIs and automated scraping of PDFs/XLS/web portals). All records were standardised to megawatt-hours (MWh), and aligned to local-calendar daily totals (i.e., midnight-to-midnight in local standard time).</p> <p>To support and encourage transparent downstream use, we also provide the raw extracted series, alongside harmonised daily aggregates, metadata, and our processing and scraping scripts. We also publish diagnostics quantifying completeness, gaps, and outliers flagged using a range of statistical methods. Independent validation against Ember monthly electricity demand shows strong agreement in temporal variability for most countries.</p> <p>Our open dataset will enable regional and cross-country analysis of demand seasonality, growth and variability; evaluation of weather–demand sensitivity using reanalysis or forecasts; and event-based studies of disruption and recovery during extremes. We finish with a short case study application of our dataset and discussion on how it should and should not be used.