Energy Structure and Multiple Environmental Outcomes: Cross-National Panel Evidence from a Country-Level Study

National energy systems are routinely linked to environmental performance through a single energy measure and a single outcome, usually carbon dioxide, leaving the breadth of that relationship untested. Using a balanced panel of 120 countries observed annually over 2011–2020 (1200 country-year observations) from the World Development Indicators, six energy variables are related—the renewable, fossil, and nuclear shares, energy intensity, electricity access, and electric power per capita—to five environmental outcomes: per-capita CO2 and methane emissions, PM2.5 exposure, forest area, and freshwater withdrawal. Every outcome is estimated under the same ladder of estimators: pooled regression, two-way fixed effects with Driscoll–Kraay standard errors, instrumental variables, and Blundell–Bond system GMM. The energy mix explains carbon emissions strongly (R2 = 0.73) and air pollution moderately (R2 = 0.42) but accounts for little variation in freshwater withdrawal (R2 = 0.06). Holding the renewable and nuclear shares and energy intensity constant, the fossil-fuel share carries no independent association with per-capita CO2; this counter-intuitive null is reported openly and attributed to collinearity among competing shares of one supply mix, together with a measurement limitation in the underlying series, rather than to any emission-reducing property of fossil combustion. A higher renewable share is associated with lower per-capita CO2 within countries and, cross-sectionally only, with greater forest cover; it shows no robust within-country association with air quality or freshwater withdrawal, and, in the dynamic specifications that pass the Hansen and AR(2) diagnostics, estimates attenuate because the outcomes are highly persistent. Cleaner energy is associated with lower carbon, not with uniform improvement across environmental dimensions.