Changes in U.S. Residential Monthly Energy Use per Capita: 1990-2017

Residential energy consumption represents a large share of total end use energy and shows strong correlation with monthly cooling and heating degree days. This study focuses on quantifying temporal change in the relationship between monthly degree days and monthly U.S. residential use of electricity and natural gas for each of the 48 contiguous states from 1990 to 2017. We introduce a single degree day predicator to characterize the non-linear relationship between degree-day and state-level electricity and natural gas use. By looking at trends in three DD-energy use coordinates and curvature from single quadratic fits on a year-by-year and state-by-state basis, we confirm the non-linear relationship between DD and residential energy use and reveal processes that might influence the relationship. We find that residential electricity energy use has become more sensitive to seasonal fluctuations in temperature in most states. While the lowest electricity use per year has risen, natural gas use has fallen since 1990 in most states. We further group the states into 17 classes for electricity use and 21 classes for natural gas use based on combinations of temporal trends in quadratic curve variables. These large groupings for electricity have shown a similar spatial distribution as that of the climate regions defined by the U.S. Department of Energy, reaffirming temperature and humidity as influential factors in the climate-energy relationship. We also compare our results with the household and end uses information from U.S. Energy Information Administration’s Residential Energy Consumption (REC) Surveys and recognize electricity as a growing heating source in all U.S. regions. We further address economic development, energy efficiency of end uses, and building codes as potential trends that affect the relationship between degree day and residential energy use at national, regional and state levels.