Key Points • NRLSSI2h solar irradiance variability model with 0.1-0.5 nm resolution captures larger UV. spectral line variability relative to continua. • At 300-400 nm, dominated by spectral features, NRLSSI2h estimates 2-5X smaller solar cycle variability than radiative transfer models. • Upper atmosphere solar radiation absorption can differ using NRLSSI2h (e.g., 34% decrease at 88 km for Lyman alpha).