Variation in estimates of the footprint of large, ground-mounted photovoltaic solar energy in the United States and its associated land-cover change across three datasets

Solar energy contributed more than six percent of the United States' (US) energy generation capacity in 2022, predominantly from large, ground-mounted photovoltaic solar facilities (GPVs). That proportion is expected to increase as GPV development accelerates and its land footprint expands. This study compared and harmonized three datasets describing the US GPV footprint, evaluated the land-use and land-cover change associated with each, and identified their best use cases. Two publicly available datasets delineated photovoltaic panel arrays, while a third paywalled dataset mapped the broader GPV fence line. For GPVs represented in all three datasets, we harmonized the data to 2018 and calculated both footprint area and quantified the footprint area and that of the land-cover classes converted within it. Our results suggest that US GPV footprint estimates from the panel array datasets are up to 34 % smaller than those from the fenceline dataset. This has implications for land-cover change estimates; conversion of the relatively undisturbed categories shrubland and scrubland was 8 % higher in the fenceline dataset than in the array datasets. As such, due to differences in their definitions of "footprint" and footprint delineation methods, these datasets are not interchangeable and have specific analytical contexts where they are best suited. A lack of publicly available data describing the broader GPV footprint hinders analysis of the relationship between GPVs and other place-based phenomena, particularly considerations of land-cover change and its relationship to biodiversity conservation.