In many developing countries large parts of the population are negatively affected by the lack of access to clean and affordable energy. Providing sustainable energy services to these people has been acknowledged as a key component to reduce poverty. One form of development assistance to address the needs of the energy-poor at the local level are small-scale renewable energy projects. Like all development interventions, these energy projects are not intended to produce short-term outputs, but to create long-term impacts. Thus, it has become increasingly important to evaluate and accurately assess their sustainability. But despite the widely recognized need to identify successes factors and explain failure only few studies exist that address the sustainability of small-scale of energy development efforts post implementation. Against this background the paper presents the results of a post-evaluation of 23 projects supported via the Sustainable Energy Project Support (SEPS) scheme of the WISIONS initiative run by the Wuppertal Institute. The analysis provides insights on the influence that socio-economic, environmental, geographic and gender factors can have on the sustainability of small-scale renewable energy projects in developing countries. (C) 2014 Elsevier Ltd. All rights reserved.