Solar and wind energy today have a significant role in providing carbon-free electricity to European systems, and their importance is expected to increase in the next decades while the entire continent aims to reach carbon neutrality. The availability of wind and solar energy is directly linked to meteorological conditions and the two sources show thus a natural variability, but also complementarity. This study provides an analysis of this phenomenon based on the most recent data for the year 2020 provided by all the European electricity transmission system operators. The analysis focuses on the countries where this phenomenon is more evident, which are large enough to play a dominant role for generation and demand in Europe and/or where the wind & solar energy have a higher share in the energy mix, namely France, Germany, Italy, Spain, and United Kingdom. The presented results indicate that patterns of complementarity differ strongly among investigated countries: southern countries produce relatively more power in summer months compared to winter months than the United Kingdom and France. In fact, United Kingdom, Germany, and France have a stronger summer–winter difference in capacity factors of wind and solar than Spain and Italy. From the power system perspective, the resource complementarity might be beneficial assuming the possibility to transfer the surplus of low-carbon electricity via cross-border exchanges. In the summer, when wind resources are slightly worse than in winter, southern European PV generation could be transferred to the north, while the opposite is true in the winter.