Spatiotemporal Analysis of Electricity Reliability Using VIIRS Nighttime Lights: Case Study in South Africa

Electricity reliability is essential for modern socioeconomic development, yet global efforts have often prioritized expanding access over ensuring service quality. The critical dimension of service reliability creates a significant policy challenge in many developing nations, especially in South Africa which has experienced reliability crisis driven by frequent load shedding, weather shocks and aging assets. In this study, we developed a multiscale framework that uses Visible Infrared Imaging Radiometer Suite (VIIRS) nighttime lights from 2012 to 2024 as a proxy to explore electricity reliability with complementary indicators. We used index of dispersion, z-score, and annual cycling as the reliability indicators to explore the power instability in South Africa from pixel level to administrative units. Our results show strong positive correlations between the national radiance z-score and the power generation availability ( r = 0.90), and an inverse relationship with power outage metrics ( r = -0.90). Spatially, Emerging Hot Spot Analysis reveals significant clustering of instability, identifying hot spots in provinces such as Gauteng and Western Cape, contrasting with cold spots in Limpopo and North West. The annual cycling pattern is pronounced with a winter-peak in Free State, Gauteng, Mpumalanga, and North West. Load-shedding stages can dampen the annual cycling pattern as validated in Cape Town. In addition, precipitation has a modest contemporaneous dimming effect that fades by one to two months. Our findings indicate that nighttime lights can support an operational and policy-oriented dashboard for monitoring reliability across space and time.