Reliable and sustainable power supply for remote rural areas is of vital importance for development of these areas. In this paper, the techno-economic feasibility and flexibility of hybrid renewable energy systems are demonstrated under both off-grid and on-grid modes for rural electrification, where a case study of a village in West China is presented. According to simulation and optimization results as well as sensitivity analysis, the most cost-competitive configuration is found by Hybrid Optimization of Multiple Energy resources (HOMER). Comparison of the off-grid and on-grid modes of the hybrid system has been carried out. The results demonstrate that a hybrid renewable energy system which comprises solar, wind and biomass is reliable and cost-effective regarding sustainable rural electrification. Moreover, environmental and social benefits can also be acquired by this system. The high capability of the proposed flexible design is demonstrated over conditions for both off-grid and on-grid modes.