When a wind or solar plant is far from the main demand centres, the grid itself can become the bottleneck. The electricity is cheap to produce, but the wires cannot physically carry it to where it is needed. In those moments the system operator has to tell cheap renewables to stop generating and pay more expensive gas plants, closer to demand, to ramp up instead. That service is called redispatch - in Spain, Technical Restrictions. And in Spain, the bill for it has exploded. In 2020 it cost the system €528 million. In 2024 it cost €2,523 million - nearly fivefold in four years, a compound annual growth rate of roughly 48%. Post-blackout, it accelerated again. The structural case for batteries in Spain is partly the day-ahead arbitrage window. It is also, very directly, this bill.
What the bill actually pays for
Technical Restrictions is the service REE calls when the economic market dispatch - day-ahead clearing plus intraday adjustments - does not respect some physical limit on the grid. The limit is typically a thermal constraint on a congested corridor, a voltage-control shortfall in a sub-area, or a synchronous-inertia shortfall during a high-renewables hour. To rebalance, REE instructs renewables to curtail inside the constrained zone and ramps up combined-cycle gas (CCGT) or cogeneration in neighbouring zones. Both legs cost money: the renewable operator is compensated for the energy it could have sold, and the thermal operator is paid above merchant to run. The difference between what the system paid and what the pure economic dispatch would have cost is Technical Restrictions.
The trajectory
REE’s published ESIOS settlement data show a near-exponential increase in the Technical Restrictions component of the final electricity price. 2020 closed at roughly €528 million, averaging €1.4 million per day. 2021 was €851 million. 2022 reached €1,390 million, driven partly by exceptional gas prices but also by a step-change in congested hours. 2023 hit €1,940 million and 2024 closed at €2,523 million - roughly €6.9 million per day on average. In the months following the 28 April 2025 blackout, average daily redispatch spend climbed to roughly €15 million per day as REE tightened its operating envelope. In aggregate, adjustment services added €11.43/MWh to the final Spanish electricity price in 2024 - an uplift on the order of 11% over a typical wholesale clearing price.
Why the number is growing
Three forces compound. First, the renewable pipeline has grown faster than the grid-reinforcement pipeline - there is more renewable capacity asking for access to the same transmission corridors, so congestion hours rise non-linearly. Second, the retirement of legacy thermal plant and the closure of several nuclear units under the 2027–2035 phase-out reduce dispatchable capacity in exactly the zones where Technical Restrictions are most often called. That forces REE to pay a higher redispatch premium to secure the remaining thermal fleet. Third, post-blackout REE has tightened synchronous-inertia and dynamic-voltage requirements, which expands the set of hours where renewable-heavy dispatch cannot be accepted as-is.
Why BESS is the natural substitute
For most of the Technical Restrictions envelope, a battery does the same physical work as a redispatched CCGT: it injects or absorbs real power at a specific node at a specific minute. In grid-forming configurations it can provide synthetic inertia and voltage support as well. Unlike a CCGT it does not have a ramp constraint, does not require gas, does not emit CO2, and does not need to warm up. Grid-forming inverters - which MITECO’s €300/kWh bonus in the €700M scheme is explicitly designed to catalyse - close the last functional gap between batteries and synchronous machines on voltage-support services.
The economic substitution logic is direct. If a CCGT is being paid €150/MWh to run out-of-merit to lift a transmission constraint, a battery placed at the same node that can discharge into the constraint does the same job. The difference is that the battery then recharges in a low-price hour, whereas the CCGT burns gas. Over a year, the battery’s all-in cost of relieving the same constraint is materially lower. As BESS fleets scale, the merit of the Technical Restrictions stack shifts toward batteries.
What the number tells developers
The Technical Restrictions bill is the single clearest quantitative signal that Spain has a flexibility deficit, and that the TSO is currently paying for it in cash. MITECO is under explicit mandate under Royal Decree 997/2025 and the CNMC’s adequacy review to route some of that spend into new storage. For a developer siting a project, the practical question is no longer “will BESS be needed?” but “which substations sit inside REE’s most expensive Technical Restriction zones in 2024–2025?” That is a public data layer (ESIOS zone-level settlements), and it is a much better first filter than the grid-access queue alone.