Historical Patterns for Rooftop Solar Adoption Growth Rates in Connecticut

Although the opportunities for rooftop solar to provide clean, reliable power are transformative, the benefits might not accrue to all communities evenly. National studies have exposed disparities in rooftop solar adoption across demographic groups, with low-income, renter-occupied, and communities of color disproportionately participating less. To better understand the mechanism that led to the observed national disparities, this paper explores solar adoption growth rates, using Connecticut as a case study. Connecticut stands out for the state’s early effort to broaden access to rooftop solar, specifically to low-and moderate-income residents, through incentive projects under their Residential Solar Investment Program (RSIP). Combining time-series data on the location of existing rooftop solar systems from Connecticut Green Bank and demographic information from the American Community Survey, rooftop solar adoption growth rates are calculated using a logarithmic growth function and compared across household income, home ownership, and racial and ethnic lines. After implementation of the RSIP, we find that the average observed growth rate in rooftop solar adoption doubled throughout the state, while the previously observed adoption disparities by home ownership and race/ethnicity were greatly reduced. This analysis suggests the potential effect of appropriate solar policies to reduce economic and racial disparities in rooftop solar participation.