Off-grid renewable energy technologies are important in improving electricity access for rural communities. However, methods for ensuring their sustainable operation are often poorly understood. In this article, existing approaches for the assessment of off-grid projects are examined. Reliability of the technology, financial viability and community engagement are identified as the 3 key areas governing the sustainability of projects. Focusing on these areas, a methodology is proposed to understand the sustainability of micro-hydropower plants. A mixed-methods approach including a maintenance assessment and interviews with managers, operators and consumers is used to evaluate 24 sites in Nepal. Technically, the results of the study showed that trained operators delivered a higher standard of maintenance, however, technical issues were identified that arise during the design, manufacture and installation phases. The financial viability of plants was aided by charging consumers based on consumption, whilst plants with a higher rated capacity tended to benefit from a larger number of productive end uses. Community engagement was fostered through the local identity of the plant however this was threatened by societal changes. Inherent features of the site, such as rated power and the population density, internal resilience to short-term shock events (failure of components, insufficient collection of tariffs and departure of trained operators) and long-term external development (increased incomes, increased energy consumptions and growth in rural settlements) were found to affect the sustainability of plants.