© The Author(s) 2020. This article discusses the social development practices of an international collaboration working to reduce energy poverty through the provision of household solar lighting for Indigenous people living in remote communities in the Remexio district in Timor-Leste. The article discusses some of the findings of a practice-based study that uses collaborative inquiry to analyse the working model of ‘Lampu Diak’, the name of the solar lighting project, and its impacts on the health and well-being of local people and the communities in which they live. Underpinned by a practice-based sociomaterial approach, the analysis characterises the Lampu Diak project as a heterogeneous and distributed network. It discusses four of the developmental social work practices that sustain the project, with a particular emphasis on the introduction of clean, affordable, sustainable solar lighting and the associated ‘common funds’. Common funds are informal microcredit schemes managed by community-based self-help groups. The article explores the potential affordances, benefits and pitfalls of common funds and the unanticipated ways in which they continue to unfold and extend the Lampu Diak project. The article contributes an example of how a village-to-village transnational collaboration practises developmental social work in a particular context.