The champion 50–50 strategy against renewable energy droughts in Europe

Power systems with growing shares of wind and solar are increasingly exposed to weather-driven generation deficits, yet robust strategies to reduce renewable energy drought risk remain unclear. Using 1950–2025 pan-European capacity factor data and a threshold-free intensity–duration–frequency framework across European countries, we quantify drought risk under alternative wind–solar mixes. We find that balanced portfolios centered around 50% wind and 50% solar consistently perform near the optimum across countries, severities and event durations, capturing most of the achievable resilience gains. The remaining risk is concentrated in winter and associated with a limited set of blocking and NAO-like circulation regimes. These results identify a simple and physically grounded design principle for more climate-resilient renewable power systems.