Solar and wind time variability may be mitigated by complementing each other, providing firm power to the national grid at local and regional scales. The field commonly utilizes reanalysis data; however, it is crucial to conduct bias analysis and validation to enhance reliability. Mexico's vast geography and resource potential demand a comprehensive study to validate the accuracy of modeling critical meteorological variables in power estimations. This study explored wind and solar resources' local and regional complementarity using experimental and ERA5 data. A bias-correction method was used to identify bias effects on power estimations and the reliability of long-term capacity factor analysis. Spearman's coefficient was used as the complementarity index. The results show that the capacity factor of wind turbines is affected by bias-correction methods compared to that of photovoltaics. Spearman's coefficient, in general, is robust over bias-correction. The Yucatan Peninsula displays significant potential throughout the year, Spearman −0.6, for combining offshore wind farms with onshore photovoltaics. During summer, the north-central, northeast regions and the Baja California Peninsula offer significant potential for combining wind and solar energy, −0.6 and −0.5 values, respectively. Incorporating renewable energy requires further analysis of local integration and technical limitations to create sustainable long-term solutions.