Electricity prices in Spain frequently experience periods of lower wholesale spot pricing during times of high renewable energy generation, driven by the country's massive investments in solar photovoltaic and wind power infrastructure. When weather conditions favor high renewable output, clean generation floods the regional grid at near-zero marginal costs. However, overall retail bills can still fluctuate significantly due to regulated capacity tolls, environmental taxes, and the marginal pricing design where natural gas backup plants set the final rate during peak demand windows.