A global feasibility gap in resilient island energy transitions.

Island nations are central to achieving United Nations Sustainable Development Goal 7 on affordable and clean energy, yet the feasibility of their energy transitions remains poorly quantified. Here we show, using a high-resolution assessment of over 1800 inhabited islands and 50 million hourly records of demand and renewable resources, that resilient low-carbon power systems remain out of reach for many islands. More than half of the islands assessed face transition costs above income-based affordability thresholds, with the greatest burdens in Southeast Asia, coastal Africa and the Western Pacific. Adding climate-resilience requirements moves 7% of islands into higher-cost categories. Although technological progress could lower average levelized cost of electricity by about 4% by 2050, this reduction is too small to close the feasibility gap for low-income islands. These findings show that market-driven cost declines alone are unlikely to deliver equitable island energy transitions, and that targeted support is needed.