Growth in energy justice: Exploring impacts of Residential Solar Incentive Program on rooftop solar adoption growth rates in Connecticut

Solar photovoltaics (PV) offers an alternative to fossil fuels and accelerated adoption of solar PV is expected among utilities, businesses, and communities. However, not all communities are seeing these transformative opportunities. 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 across demographic variables, 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 participation in rooftop solar opened up to new communities and that the median observed growth rate in rooftop solar adoption doubled throughout the state. This analysis suggests the potential effect of appropriate solar policies to increase state-wide adoption while reducing economic and racial disparities in rooftop solar participation.