This paper deals with the design of an electrical supply off-grid for a remote village without access to a utility grid and with very low incomes in Northern Laos. Environmental issues and cost minimization lead to ahybrid system composed of pico/micro hydroelectric turbines, PV panels, a water reservoir as an energy storage device and a backup genset. The annualized least cost of energy is optimized thanks to a genetic algorithm (GA). The forced outage rates (FOR) of pico and microhydro turbines are taken into account in the optimization process. Finally, the results of the system sizing are presented and compared.