Distributional disparities in residential rooftop solar potential and penetration in four cities in the United States

Single-family residential rooftop solar adoption in the United States has not occurred equitably across the country, nor across socioeconomic and demographic groups. In response, state and local governments have developed solar equity programs, primarily focused on increasing adoption by low- and moderate-income (LMI) households. This study merged national datasets that estimate rooftop solar potential, the distribution of rooftop solar systems, and census tract- level socioeconomic and demographic characteristics to answer three questions. First, how are spatial distributions of rooftop potential and penetration similar and different across cities? Second, how is rooftop penetration distributed across non-LMI and LMI communities in different cities? Third, how do the relationships between rooftop penetration and local socioeconomic and demographic characteristics, identified as barriers to solar adoption, differ? Using GIS, bivariate and multivariate analyses, these questions were examined in four US cities - Riverside and San Bernardino, California, Washington, DC, and Chicago, Illinois - to understand both universal and distinct local manifestations. Findings include: higher rooftop potential existed in some LMI communities; higher rooftop potential did not necessarily translate to higher rooftop penetration, especially if higher potential was in LMI communities; and beyond income, other socioeconomic and demographic characteristics such as race/ethnicity, limited English proficiency, age of housing stock, and internet access were associated with rooftop penetration. While there remains great potential for expanding rooftop solar to LMI households and communities, understanding the local dynamics of solar potential and penetration may inform better policy development and implementation.