Spain curtailed excess electricity during the summer of 2026 because demand could not absorb it, while grid constraints limited the system’s ability to handle installed capacity. Nuclear power has regained a role the government had planned to reduce.
The immediate problem is operational. Spain has more installed capacity than its grid can effectively manage, leaving new renewable facilities struggling to secure connections and earn the income they expected. Data centres have brought the constraint into sharper focus. Government regulations have imposed requirements that new industrial users find difficult to meet, rather than clearing the way for additional connections.
Aelec says 83.4% of Spain’s distribution network nodes are already saturated.
That is the contradiction at the centre of Spain’s green transition: generation is expanding while access to the network is narrowing. Infrastructure constraints reportedly prevented 66% of declared electricity demand from being met in 2024.
The pressure has shifted the timetable for nuclear power.
In the summer of 2026, electricity companies asked to extend the operation of both Almaraz reactors until June 2030. Spain’s Nuclear Safety Council assessed the request, which was accepted. The decision delays the closure of the first reactors scheduled to leave the system. It is intended to help balance the grid as renewable generation grows.
Keeping Almaraz online also limits reliance on gas. Gas-fired generation can push electricity bills higher when the system needs extra support, making the reactors part of the effort to manage the mismatch between supply and network capacity.
CEOE supported extending Almaraz, calling the move the fulfilment of a longstanding business demand. Sources linked to Red Eléctrica see a beneficial but limited effect on the power system: the extension does not resolve the structural shortfall in network infrastructure.
The political backdrop was set by the blackout of 28 April 2025, when the Iberian Peninsula was left without electricity for almost an entire day. The outage put Spain’s infrastructure under direct scrutiny and turned network ability to recover from a technical issue into a central test of energy policy.
The blackout investigation has moved beyond a purely technical dispute. Spain’s competition regulator CNMC is preparing its first sanctions. Some alleged breaches may have existed long before the outage. Energy companies say they lack data showing improper disconnections during the blackout, while Red Eléctrica has called for a fuller, more technically grounded analysis from them.
During Pedro Sánchez’s second term, the Ministry for the Ecological Transition was first led by Teresa Ribera and later by Sara Aagesen. Both pursued a continuity agenda focused on the green transition. Aagesen’s tenure was shaped by the blackout and the difficulty of integrating rising renewable production into a network unprepared for current demand.
Red Eléctrica operates the system, while the government controls infrastructure planning. That split leaves the country with a practical constraint: generation can be added faster than the connections and flexibility needed to use it. The figures cited by Aelec point to systemic restrictions, not just a few isolated local bottlenecks.
The emissions data add to the pressure. Red Eléctrica reported 21.2 million tonnes of CO2 equivalent during the first nine months of 2026, 3% more than in the same period a year earlier. The increase followed a reinforced operating mode designed to strengthen the electricity mix. Emissions had already risen by 9% before that latest deterioration.
Transport is moving in the wrong direction as well. Spain is expanding renewable capacity without delivering a comparable reduction in emissions.
An earlier report on renewable gas projects showed the same infrastructure risk: investment can advance on paper, but the network determines whether new capacity can operate profitably.
Spain now faces a connection problem alongside its generation push. The Almaraz extension shows that nuclear power has returned as a practical balancing tool. Record curtailment and higher emissions expose the cost of a network that has lagged behind policy ambition.
The decision does not formally cancel Spain’s nuclear phase-out. The government still plans to close the country’s nuclear fleet by 2035 while allowing Almaraz to operate until June 2030. Nuclear capacity so remains in the system as the grid stays saturated and demand for dispatchable generation rises.
The government’s energy strategy has accelerated generation without providing enough network capacity to turn that expansion into reliable, cleaner electricity.
