Spain has a high potential for renewable energy production, being the world's third country by installed on-shore wind power. However, it has not yet fully developed its renewable energy production capacity, with no commercial offshore wind production to date, and remains highly dependent on fossil fuel imports. The country is also one of Europe's most biodiverse, on land and at sea. This study spatially assesses the country's offshore wind energy potential by incorporating the newly designated marine protected areas (MPAs) to the official Spanish strategic environmental assessment for the installation of offshore windfarms (SEA). It also identifies optimal areas for offshore windfarm development according to key physical variables such as wind speed, depth and substrate type. It finally assesses real commercial windfarm projects against current environmental constraints. The results show that nearly 50% of the whole area within 24 nm from the Spanish coast could be suitable for offshore windfarm development at the planning phase. However, only 0.7% of that area is optimal for wind energy production with current fixed turbine technology. Nevertheless, either area would allow Spain to meet its national targets of 750 MW of ocean power capacity installed by 2020 under adequate local wind conditions. Over 88% of all commercial windfarm project area is within the SEA's Exclusion zone, thus unfeasible under current circumstances. Technological breakthroughs like floating turbines may soon make the optimal windfarm area (OWA) less restrictive and reduce current environmental impacts of marine windfarms within a truly sustainable Blue Growth.