Understanding the location and potentialof renewable energy resources is a crucial pre-requisite totheir utilization, and to scaling up clean and securesources of electricity generation such as biomass, smallhydropower, solar, and wind. However many countries do nothave high quality, publicly available data on renewableenergy resource potential and this limits the potential forinformed policy development, including zoning guidance,transmission network planning, and price regulation orincentives. It also narrows the field of potentialcommercial developers, and raises the cost of undertakingpreliminary site identification and financial analyses. Thisreport draws on many years of experience within the WorldBank Group and among other development partners in carryingout renewable energy resource assessment and mapping at thecountry level, in particular from 12 projects funded by theEnergy Sector Management Assistance Program (ESMAP) under amajor global initiative launched in 2012. The report’spurpose is to explain, for a wide range of audiences, theimportance of resource assessment and mapping, key steps andgood practices, methodological issues, and potential sourcesfor further advice and support.