This paper evaluates how operation and maintenance (O&M) factors affect energy production and optimal deployment sites for floating offshore wind farms (FOWs) in the North Sea and the Iberian Peninsula. The geospatial analysis incorporates reliability, maintainability, accessibility, and availability aspects, and evaluates their impact on energy production. The results demonstrate that O&M factors have a significant impact on the final energy production and therefore on the identification of optimal deployment sites, both quantitatively and qualitatively. In the North Sea, promising deployment sites are identified in regions with lower wind resources but shorter turbine downtime, such as Denmark, Germany and southern Scotland. In the Iberian Peninsula, areas with high resource potential, such as the northwest Spanish and Portuguese coasts, may be less appealing than the less powerful Mediterranean regions due to lower maintainability. In particular, the efficiency of future FOW farms in the North Sea and Atlantic Ocean regions of the Iberian Peninsula heavily relies on vessel operational limits for major repairs. Increasing the significant wave height limit for major repairs from 1.5 m to 2 m results in an average capacity factor increment of 2.54% across ScotWind farms and over 6% along the northwest coast of the Iberian Peninsula.