Background and Objective: Given the growing importance of sustainable development in the face of environmental degradation, climate change, and rising energy demand, this study investigates the heterogeneous impacts of renewable energy, clean energy access, industrialization, and institutional quality on the Sustainable Development Index (SDI) across selected BRICS countries and Iran over the period 2004–2022. Emerging economies face a dual challenge: they need to sustain economic growth and industrial expansion while mitigating the environmental pressures stemming from fossil fuel dependency. The core research question is whether these variables exert uniform effects across different quantiles of the SDI distribution or exhibit structural heterogeneity.
Methodology: To test the hypothesis and examine the impact of explanatory variables across various levels of the sustainable development distribution, the Simultaneous Quantile Regression (SQREG) method is employed.
Results and Findings: Empirical findings indicate that renewable energy exerts a positive and significant impact at the lower deciles of the SDI, whereas access to clean cooking fuels and technologies plays one of the most consistently positive roles across all quantiles. Industrialization exhibits a negative and significant effect at the lower deciles, which is moderated and weakens as the level of sustainable development increases (higher deciles). Inter-quantile Wald tests confirm the presence of structural heterogeneity and significant slope differences across the distribution. The results underscore the necessity of adopting strategies tailored to countries’ levels of sustainable development, including expanding access to clean technologies, targeted support for renewable energy, and steering industrialization toward low-carbon pathways.