Decarbonizing U.S. power systems under extreme heat: Solar–wind penetration and multi‐pollutant emission performance

Abstract

Extreme heat increases electricity‐system stress, but its influence on the relationship between renewable penetration and emissions intensity remains insufficiently understood. This study evaluated heat‐conditioned associations between observed solar–wind penetration and consumption‐based CO ₂ , NO _x , and SO ₂ intensities across seven U.S. balancing authorities during 2019–2024. Hourly EIA‐930 operations, Open Grid Emissions data, and NASA POWER meteorology were integrated into 15,211 complete balancing‐authority‐day observations. Region‐specific heat thresholds were established using 2019–2023 data and retained unchanged for a separate 2024 assessment. Two model‐derived indicators, Emission Displacement Effectiveness (EDE) and the Heat‐Stress Decarbonization Performance differential (HSDP), were used to quantify and compare renewable–emissions associations across operating regimes. Extreme‐heat days were associated with 12.99% higher electricity demand during 2019–2023 and 14.19% higher demand in 2024. A 10‐percentage‐point increase in renewable penetration was associated with 13.53% and 14.60% lower CO ₂ intensity under normal and extreme‐heat conditions, respectively, during 2019–2023. Corresponding estimates for 2024 were 14.88% and 16.00%, yielding closely reproduced CO ₂ HSDP values of −1.07 and −1.12 percentage points. SO ₂ also exhibited negative heat differentials across both periods, whereas NO _x responses were less temporally consistent. Regional and technology‐specific estimates revealed substantial heterogeneity. The findings indicate that extreme heat did not weaken the pooled inverse renewable–CO ₂ intensity association within the examined systems. EDE and HSDP provide observational screening indicators for evaluating heat‐conditioned emissions performance, without implying causal displacement or improved physical conversion efficiency.