This article examines the significance of hydroelectric mini-grids owned and operated by Catholic sisterhoods in rural Tanzania, situating them within a broader context of energy transition and environmental justice. The Tanzanian state is betting that mini-grids can effectively supplement the national grid’s limited reach; since 2010 it has invested considerable effort in developing a regulatory framework that streamlines licensing procedures and specifies feed-in tariffs. Today, the field is wide open and a range of ownership models – community, private, state-owned – are unfolding on the ground with variable results regarding their financial sustainability, environmental impact, and developmental outcomes. Though often overlooked in this discourse, missions, churches, abbeys, and convents have a history of operating run-of-the-river power stations and other off-grid systems that stretches back into the colonial era. Such infrastructures anchor material and spiritual economies of rain, care, and cash that straddle both community and commercially oriented modes of provisioning. Their continued presence suggests that in some ways this new paradigm of decentralized energy provision builds upon long-standing historical logics of patronage and political authority in marginal areas.