With more than a billion people lacking access to electricity, local power-generation solutions are essential to provide sustainable energy to all - particularly those consumers expected to remain isolated from national or regional grids for the foreseeable future. Renewable power generation provides low-cost solutions to bring reliable electricity to rural households or island communities off the main grid. But while off-grid renewable energy systems are expanding rapidly on the ground, data that systematically tracks this progress remains limited. This working paper from the International Renewable Energy Agency (IRENA) provides an overview of current data sources for off-grid renewable energy systems. It suggests methodological improvements to help categorise such systems, evaluate and aggregate data and measure progress in deployment. The working paper comes as IRENA’s contribution to the Global Tracking Framework of the Sustainable Energy for All (SE4ALL) initiative.