For communities across sub-Saharan Africa, a consistent and affordable supply of electricity can open new possibilities for socioeconomic progress. Mini-grids—electrical generation and distribution systems of less than 10 megawatts—can play a role. These decentralized technologies are expected to bring power to 140 million Africans by 2040. Tanzania is a regional leader in mini-grid development. In 2008, it adopted a groundbreaking mini-grid policy and regulatory framework to encourage investment in the sector. Since then, the number of mini-grids in the country has doubled. The national utility (TANESCO), private businesses, faith-based organizations, and local communities now own and operate more than 100 mini-grid systems. Energy leaders across the region can learn from the country’s experience. This report is the first major survey of Tanzania’s mini-grid sector. In it, shed light on lessons from Tanzania that can help accelerate mini-grid deployment across countries in sub-Saharan Africa. This comprehensive study will be valuable to the large and growing community that is banking on mini-grids to transform energy access in Africa.