The interest in offshore wind energy is fundamentally based in most cases on the exploitation of the high levels of wind power found in offshore areas. The evaluation of marine spaces for planning and exploitation of this type of energy source is even more important in territories with isolated and/or weak electrical systems and limited available territory. In the study developed in this paper, GIS-based techniques are applied to identify priority zones for the exploitation of offshore wind farms in the islands of Gran Canaria and Tenerife, the two largest of the eight islands that make up the Canary Archipelago (Spain). The zones identified are prioritized and differentiated by the most viable type of wind turbine substructure technology (bottom-fixed or floating), capacity factor (in MWh/MW), and specific cost (€/MWh). The results are expressed in map form, which can form part of future energy planning processes for the islands. The resulting identified offshore priority zones comprise 375.9 and 68.2 km2, with bottom-fixed: floating surface area ratios of 1:6 and 1:21, for Gran Canaria and Tenerife, respectively. The method developed in this paper is vital for detailed energy planning, an important aspect in the optimization process of offshore wind energy integration in isolated and/or weak electrical systems.