Characterizing wave climate is crucial for coastal and offshore engineering applications. Reanalysis models, such as ERA5, are increasingly used due to their efficiency and lower costs compared to in situ measurements. However, their accuracy has not been thoroughly examined. This study addresses this gap by calibrating wave data from the ERA5 dataset with the available years of measurements from wave buoys in the Central Mediterranean Sea, specifically near Ponza, Cetraro, and Civitavecchia. A calibration approach was developed to adjust ERA5 wave data by aligning the model predictions closely with the co-located wave buoy observations. Results indicate that ERA5 systematically underestimates significant wave heights and periods, leading to an underestimation of wave power by up to 42% compared to buoy data. Calibration improved alignment between ERA5 and buoy measurements, enhancing wave energy representation and increasing estimated wave power by 35–48% annually. These findings underscore the importance of calibrating reanalysis datasets like ERA5 with in situ data to accurately assess wave energy potential, particularly in regions where model data may not fully capture local wave conditions. The outcomes provide valuable insights for wave energy projects in the Central Tyrrhenian Sea and similar semi-enclosed seas.