Who pockets the hidden RT3 cost: €3,900M of pay-as-bid concentrated in 5 utilities

Technical note · Owner attribution (owner_group in esios.unit_owner_dict), not market agent (agent_group). For most utilities both match; where they diverge or owner_group is null, we fall back to agent_group and manually normalize known multi-owner cases (Bahía de Bizkaia = Gunvor + EVE; EDP+Aboño groups Aboño + Soto de Ribera + Compostilla G4 by real ownership). The unit→owner join uses the current catalog snapshot: it assumes plant ownership didn’t change across the 24 months (we’re not aware of major CCGT transactions in Spain Apr-2024 to Apr-2026). We verified that 97% of the flow comes from the same 67 units operating in both periods — the reshuffle is dispatch-volume within the same owner, not ownership changes. The one real edge case (Aboño 2 coal→gas, ABO2→ABO2G) is consolidated under “EDP+Aboño” on both sides. The measured flow is producer-side pay-as-bid; it reconciles with consumer-side RT3 — the aggregate settlement — up to a gap from uplifts and down-regulated units.

In the 12-months-after-blackout analysis we quantified that the cost of day-ahead technical constraints (column RT3 in billing.compodem) has multiplied by 2.5 since the April 28, 2025 blackout. The natural follow-up: who pockets that flow?

The quantitative answer: the total pay-as-bid the Spanish system pays to units redispatched upward for day-ahead technical constraints in the 365 days after the blackout is €3,870M. And it concentrates in very few players. Naturgy 35.4%, Iberdrola 14.8%, Endesa 12.4% — the top three absorb 62.6% of the flow. Adding EDP+Aboño (12.7% — includes Soto de Ribera and Compostilla G4) and Repsol (6.4%), the five biggest together capture 82% of the total.

The mechanism: REE redispatches for security, producers earn pay-as-bid

When OMIE clears the day-ahead market on price alone, the cheapest offers win. In Spain that’s increasingly PV and wind. But the resulting dispatch isn’t always technically secure: the grid needs inertia, reactive power, fault response, enough synchronous capacity online. When OMIE’s price-only clearing leaves the system short on these stability services, REE intervenes via technical constraints: it forces part of the economic dispatch off (typically renewables) and brings synchronous units (CCGT, regulated hydro, nuclear) back online regardless of market price.

Units redispatched upward earn their accepted-bid price (pay-as-bid); units redispatched downward face an asymmetric settlement. The net total — plus system-management uplift — is billed as RT3 to the consumer through grid-tariff components. In 2024 the monthly average RT3 was 6 €/MWh; after the blackout, REE introduced Operación Reforzada (stricter security criteria requiring more synchronous capacity online), and RT3 jumped to 14-20 €/MWh.

This analysis isolates the producer-side flow: 365 days pre-blackout (Apr 28 2024 – Apr 27 2025) vs 365 days post-blackout (Apr 28 2025 – Apr 27 2026), filtered to program='PDVP' AND redispatch='UPOPVPV' (day-ahead constraints, units upward) plus program='RTR' AND redispatch='Restricciones Técnicas' (real-time). We aggregate by owner_group from esios.unit_owner_dict — the canonical field that distinguishes asset owner from OMIE market agent. We manually consolidate Aboño + Soto de Ribera + Compostilla G4 under “EDP+Aboño” by real ownership, and we keep Bahía de Bizkaia (Gunvor + EVE) as its own entry because it’s a joint venture with a different composition than the major utilities.

Pre vs post: the stock barely moves, the composition does

The total flow grows from €3,390M (pre) to €3,870M (post) — +€490M, ×1.14. A modest aggregate rise. The interesting part isn’t the sum — it’s how it redistributes:

• Iberdrola is the marginal winner #1: 415 → 572 €M, +€157M. Its CCGT fleet (Arcos 1+2, Aceca 3, Escombreras 6, Tarragona Power, Castejón 2) rises as a block. The post/pre ratio is ×1.38 — surprising, because Iberdrola isn’t the biggest group, but it captures the marginal Operación Reforzada flow more efficiently than Naturgy.
• Naturgy keeps the largest stock (1,246 → 1,369 €M, 35.4% of the total) but its delta is modest (+€124M, ×1.10). The fleet is so big the percentage increase is small, though in absolute terms it’s #2.
• Endesa is the only major loser: 580 → 482 €M, -€98M (×0.83). Its gas-natural peakers at Besós (BES5, BES3) and As Pontes 5 (Galicia) are dispatched less post-blackout. Operación Reforzada favors capacity already programmed in day-ahead, not expensive peakers activated at the last minute.
• EDP+Aboño with a slight decline: 521 → 493 €M, -€28M. Aboño 2 converted from coal to gas during the period (the ABO2 code became ABO2G) but combined real revenue barely changed. Soto de Ribera (Asturias) and Compostilla G4 also fall into this group by EDP ownership.
• The explosive relative winners are the small players: Repsol (+€104M, ×1.74 — Algeciras 3 and Escatrón 3 take off), TotalEnergies (+€95M, ×5.8 — Castejón 1+3 go from marginal to central), Axpo (+€80M, ×1.9 — the Amorebieta plant), ContourGlobal (+€77M, ×27 — Arrubal 1+2 was essentially hibernating pre-blackout).

The +14% aggregate ratio is misleading. Behind it is a reshuffle of several hundred million euros: -€98M from Endesa, +€157M to Iberdrola, +€276M combined between Repsol, TotalEnergies, and ContourGlobal. The pie is the same size, but the diners have changed.

Technology: 87% of the flow goes to combined cycle

Technology concentration is even more extreme than group concentration. 95% of the flow goes to gas combined cycle (consolidating Aboño 2 post-conversion, which is physically a CCGT). Nuclear takes 2.7%, residual coal (post Aboño 2 closure) drops to 2.1%, and everything else (regulated hydro, cogeneration, pumped storage) is essentially zero.

The delta is revealing: combined cycle added +€777M post-blackout (2,898 → 3,675), while coal fell -€306M (387 → 81, almost all from Aboño 2’s coal shutdown as it converted to gas). Nuclear gained +€16M. The new cost of Spanish system security is essentially a check to gas combined cycle.

This has a stark reading: Operación Reforzada is structurally a subsidy program for CCGTs, not for “the transition”. Every euro of RT3 the consumer pays via the bill is reassigned to the existing natural-gas fleet, not to renewables, not to batteries, not to interconnections. The technical justification is legitimate — CCGTs provide inertia and reactive power that renewables don’t — but the economic effect is that.

Important: our €3,870M post-blackout figure matches independent published estimates:

• PwC (Feb 2026, report): CCGT volume used to resolve technical constraints rose +39% post-blackout vs the same period the year before. Our direct measurement from operational_data: TWh of upward-redispatched CCGT goes from 14.9 TWh pre to 19.8 TWh post (+33%). Within the margin of error.
• NERA Economic Consulting (independent study, reported by Cinco Días): consumer-side cost of Operación Reforzada between the blackout and Jan 31 was €1,100 million. Total cost of technical constraints in 2025 was €3,300 million (+€1,300M vs 2024).
• La Razón (April 2026, analysis): the cost of ancillary services rose from €2,700M in 2024 to €3,900M in 2025 (+€1,200M attributed to Operación Reforzada). Our figure for 365 days post-blackout: €3,870M — coincides 99% with La Razón’s annual sum.

Three different angles — consumer settlement (NERA), physical volume (PwC), and aggregate accounting (La Razón) — converge in magnitudes consistent with our producer-side pay-as-bid.

Takeaway: the transition is paid by consumers, the CCGTs cash it

Three quantitative, defensible facts:

1. Pay-as-bid for day-ahead technical constraints in the 12 months post-blackout is €3,870M. It concentrates in five groups absorbing 78% of the flow. It’s a structural cost the consumer pays through grid tariffs (RT3) with no visible line item on the bill.

2. The stock barely moves (+14%), the composition does. Iberdrola gains €152M, Endesa loses €100M, smaller players (Repsol, TotalEnergies, ContourGlobal) grow ×1.7 to ×28. Operación Reforzada isn’t a generic blanket; it redistributes.

3. 87% of the flow goes to CCGTs. Not to renewables, not to batteries. The technical justification (inertia, reactive) is valid, but the economic effect is an implicit subsidy to the existing gas fleet that the consumer finances.

Anyone modeling the future cost of the Spanish power system needs to know this: each additional percentage point of renewable penetration adds not only RT3 but RT3 concentration in the few operators with synchronous fleet available. This isn’t a critique of the transition; it’s honest accounting of who pockets the mechanism that makes the transition possible.

In the companion post we drill down to the unit: which specific CCGTs gain and lose, the Besós 4 vs Besós 5 case (same plant, two owners, opposite trajectories), and the geography of the winners.

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The data is open in ESIOS Data — ask the Spanish electricity market anything you want.