Implications of Extended Operation at Almaraz Nuclear Power Plant for Spain's Energy Transition
The extension of the Almaraz nuclear power plant s operation until June 2030 significantly influences Spain s energy landscape, particularly in reducing short-term dependence on gas and stabilising energy prices. By allowing the plant to operate an additional 31 months for unit one and 19 months for unit two, it modifies existing capacity planning and market strategies. Both reactors contribute approximately 2094 MW of gross electrical capacity, with a 2025 net generation of around 14,752 GWh, covering roughly 7 per cent of national electricity demand.
To understand the scale of replacing this production with gas-fired generation, an estimated 27 to 30 TWh of natural gas would be required annually, assuming conversion efficiencies between 50 and 55 per cent. This considerable amount, constituting about 27 to 30 per cent of Spain s annual gas consumption for electricity in 2025, would cost approximately 1.62 to 1.8 billion euros per year at current gas prices. Additionally, capturing associated CO2 emissions avoidance, roughly 5.5 million tonnes in 2025, highlights potential environmental benefits.
The presence of Almaraz also moderates electricity prices by decreasing demand residuals during high renewable output hours. Maintaining the nuclear plant reduces the necessity for gas-fired plants during periods of low demand or high renewables, especially when fossil fuels and carbon costs are elevated. Gas futures averaging 60 €/MWh and CO2 prices around 82 €/tonne during August 2026 intensify these effects, making nuclear extension a strategic tool for price stabilisation.
However, increased nuclear capacity limits flexibility in periods of high solar and wind production, which may lead to energy waste if surplus renewable electricity cannot be adequately stored or exported. Without sufficient energy storage, grid infrastructure, and demand management, this situation could promote negative or zero prices and the cannibalisation of renewable revenues. Accelerating storage deployment and demand response measures becomes vital to maximise renewable utilisation and system stability.
Furthermore, the prolongation of Almaraz influences the future nuclear capacity outlook, with over 4000 MW of nuclear capacity scheduled for closure in 2030, including Almaraz, Ascó I, and Cofrentes. This sudden decrease in nuclear capacity poses challenges for maintaining system reliability and demands increased investments in renewable generation, storage, grid reinforcement, and demand flexibility. The year 2030 is poised to be a critical transition milestone, requiring comprehensive planning to ensure a dependable and flexible energy system.
The adjustment in Almaraz operation also prompts a reassessment of capacity mechanisms. Previously based on retiring units in 2027 and 2028, maintaining nuclear capacity until 2030 modifies the predicted capacity deficits. Updating capacity requirements is necessary to avoid underestimated security risks and to ensure sufficient firm capacity. Strategic investment in renewables and storage, alongside a robust capacity market, is essential to navigate this transition effectively.
Long-term forecasting tools like AleaGreen and AleaStorage will play a key role in formulating balanced scenarios. These tools assist in analysing the evolution of capacity, storage, demand, and pricing over several decades, informing investments to secure a resilient, low-carbon energy future. Decisive early action in expanding renewables, storage, and flexible demand will be crucial for ensuring a smooth energy transition that minimises reliance on gas and maximises renewable integration.