Energy from non-conventional renewable sources is a strategic alternative for diversification of the Brazilian electric matrix. Brazil, given its large territorial extent, geographical diversity and climate, presents a natural complementarity in the energy supply. The North and North-East regions have high energy potential due to the high incidence of solar, wind and tidal current primary sources. The availability of these sources has an intermittent feature making it necessary, in the case of isolated microgrid, a storage system to ensure uninterrupted service of the load. This feature of renewable sources makes the process of sizing the microgrid more complex, especially when a mix between diverse sources is proposed. This article addresses the problem of sizing non-conventional renewable sources wind, solar and tidal and the storage system in an isolated microgrid. In addition, a sensitivity analysis study is carried out to verify the best use of each individual source and to minimize the total cost of the system.