This study assesses the factors responsible for the success and failure of renewable energy access programs in Bangladesh, China, Laos, Mongolia, Nepal, Sri Lanka, India, Indonesia, Malaysia, and Papua New Guinea. Based on 441 research interviews over the course of four years, site visits to 90 renewable energy facilities, and focus groups with almost 800 community members in 10 countries, this study develops a series of overarching qualitative factors that correlate with programs that met their targets, sometimes ahead of schedule, and produced measurable benefits exceeding costs. The inverse of these factors is associated with programs that did not meet their targets, were behind schedule, and/or produced measurable costs exceeding benefits. It concludes by offering 10 lessons for energy analysts and development practitioners concerning appropriate technology, income generation, financing, political leadership, capacity building, programmatic flexibility, marketing and awareness, stakeholder engagement, community ownership, and technical standardization.