Solar Photovoltaics (PV) is an important contributor to a sustainable energy transition and consists of an increasingly affordable and accessible technology. Although solar PV policies in industrialized countries have mainly benefited affluent households, non-homeowner market segments often remain underdeveloped. In this paper, we review barriers and enablers for solar PV investments in non-homeowner market segments and investigate sustainability aspects of its institutional environment. We use focus group data from Flanders (Belgium) to investigate non-homeowner residential markets (including social, rental, and collective housing), public sector markets (including schools, and health and social care facilities), and commercial markets. They have in common that they are mostly governed or mediated by organizations, and that very specific regulatory and institutional conditions apply. Our main finding is that, even in times of high energy prices, the energy savings potential of solar PV is often not a sufficient condition for organizations to engage in solar PV investments. Major barriers include diseconomies of scale, split incentive problems, internal organizational barriers, and legal uncertainty. Important enablers are energy sharing frameworks and framework contracts for group purchasing. We conclude with recommendations on institutional quality, organizational capacity building, market development, mechanism design, and social justice to ensure sustainability.