Future changes in state-level population-weighted degree days in the U.S

This study analyzes future changes in population-weighted degree-days in 48 states over the contiguous U.S. Using temperature data from the NASA Earth Exchange Global Daily Downscaled Projects and population data from NASA Socioeconomic Data and Applications Center, we computed population-weighted degree-days (PHDD and PCDD) and EDD (energy degree-days, PHDD + PCDD) over the 21st century, under a business-as-usual scenario. Results show that although the rising temperature is the primary driver, population distribution and projection play undeniable roles in estimating state-level heating and cooling demand. Throughout the 21st century, the U.S. is projected to experience a heating-to-cooling shift in energy demand, with the number of heating-dominant states dropping from 37 to 17 and the length of cooling seasons extending by 2 months (indicating a corresponding reduction in heating seasons) in all states by late-century. Meanwhile, a more homogenous EDD pattern is expected due to the increasing PCDD and decreasing PHDD, and the peak EDD month will switch from winter to summer in 15 out of 48 states. Our study provides a more nuanced understanding of future heating and cooling demand by examining both annual and monthly variations in the demands and how their relative dominance in a single framework may evolve over time. The study's state-level perspective can provide valuable insights for policymakers, energy providers, and other stakeholders regarding the forthcoming shift in demand patterns and related building operations and energy consumption at both state and regional levels.