This research evaluates the impact of information sources on the feasibility of a Hybrid Renewable Energy System (HRES). Due to their isolation and low population density, island communities satisfy their demand for electricity through thermoelectric plants. Diesel is the main fossil fuel used. This fuel must be imported, which translates into high logistics and operating costs. HRES are a feasible solution, integrating renewable resources, thermoelectric plants, and energy storage systems. The proper characterization of the variability of a renewable resource is decisive in the feasibility of an HRES. We used three sources of information on solar radiation and wind speed: the NASA Power Database (Case a), results of atmospheric and solar radiation models (Case b) and prospecting campaigns for wind and solar resources (Case c). The main findings point to an undersizing in the three best solutions: PV-Diesel, PV-Diesel-Battery and PV-Wind-Diesel-Battery with data from Case a, compared to measurements on site (Case c). On the other hand, a clear oversizing of the main architectures obtained with HOMER is evidenced, when using information sources from Case b compared with data from Case c. Therefore, the feasibility of an HRES begins with the selection of the information source of local renewable resources.