Profile #3 — Castleton at Amorebieta: 5 months running at 100%

Third in the series “Profiles of the post-blackout club”. Previous posts covered ContourGlobal at Arrubal and TotalEnergies at Castejón — both with the same “hibernation → base” curve in the north-interior corridor. Amorebieta is different.

Amorebieta (AMBIETA in OMIE codes, also known as Bizkaia Energía) is an 786 MW CCGT in Amorebieta-Etxano, Vizcaya, 20 km from Bilbao. It shares coast with Bahía de Bizkaia (BBE) in the same province, both connected to the Gatika substation that feeds the northern peninsular grid.

If Arrubal was the most explosive winner in relative terms (×27), Amorebieta is the biggest winner in absolute scale: +€81M post vs pre, similar to Castejón in magnitude — but for completely different reasons. And it came at the price of a rare phenomenon: five consecutive months operating at the theoretical physical maximum.

Who Castleton is — and what Axpo is doing in the middle

Unlike the first two profiles, the ownership of Amorebieta is deliberately opaque in public records. The asset owner is Castleton Commodities International (CCI), a Stamford (Connecticut)-based trading firm operating mainly in physical commodities (gas, oil, power). CCI closed the acquisition of Amorebieta in February 2020, describing it as their “entry into the Iberian hub” and partnering with White Summit Capital AG to co-manage the investment.

But in OMIE / REE records, the unit appears under AXPO IBERIA. Axpo is a major Swiss producer and trader with deep presence in the Iberian market (one of the largest power traders in Spain and Portugal). Axpo isn’t the economic owner of the asset — it’s the market representative: the entity that bids on OMIE, manages the constraints position, and handles the relationship with REE and the broader market on behalf of Castleton.

This structure — passive industrial owner + specialist market representative — is relatively common for energy assets held by funds or pure traders. What matters for our analysis: the pay-as-bid flow reaches Castleton via Axpo and our data attributes it as “Axpo” following the DB’s canonical owner_group field (in esios.unit_owner_dict).

The trajectory: active → saturation → active

Pre-blackout (2023 through April 2025), Amorebieta is already an active unit, not hibernating:

• Typically dispatched 25-65 GWh/month
• With 130-370 operating hours per month
• Average prices €120-330/MWh

It was a normal mid-merit unit — not emergency peaker, not base load, something in between depending on the day and the system’s state. The antithesis of Arrubal.

The post-blackout switch:

• May 2025: 136.8 GWh, 733 hours (of theoretical maximum 744 in a 31-day month)
• June 2025: 134.8 GWh, 712 hours (of 720 max in 30 days)
• July 2025: 138 GWh, 744 hours — the absolute maximum, every hour of the month operating
• August 2025: 138.5 GWh, 744 hours — the maximum
• September 2025: 137.1 GWh, 644 hours (of 720)

Five consecutive months at 90-100% operating capacity. That doesn’t repeat in any other CCGT in the analysis. Arrubal, Castejón, Escatrón sustain 200-300 hours/month post-blackout. Amorebieta ran almost continuously for 5 months.

Then, abruptly, returns to normal:

• October 2025: 168 hours, 31 GWh — profile return to pre-blackout levels
• November 2025 - February 2026: 53-211 hours, 10-39 GWh

The behavior isn’t “hibernation → base”. It’s a 5-month extreme episode + return to historical behavior.

Why the 5 months?

The most reasonable hypothesis: during the first 5 months post-blackout, REE needed to ensure maximum operational redundancy for security reasons — the system was rebuilding confidence, the April 28 event was fresh, and Operación Reforzada’s strict criteria were applied with wide margin. Amorebieta, sitting in a northern coastal node with high wind penetration from the Bizkaia-Cantabria zone, was one of the machines designated to be permanently online.

From October on, once the system had demonstrated 5 months of operational stability, REE relaxed the directive and returned to a discretionary dispatch regime similar to pre-blackout. Amorebieta stopped being structurally necessary 24/7 and became a flexible actor again.

The contrast with BBE in the same province

Here’s the most revealing piece of the profile. In the same Vizcaya province, two near-identical CCGTs in size and grid connection take opposite trajectories post-blackout:

• Amorebieta (800 MW, Castleton/Axpo): +€81M
• Bahía de Bizkaia (786 MW, Gunvor + EVE): -€63M

Bahía de Bizkaia is a joint venture between Gunvor (75%) and EVE (Basque Energy Agency, 25%) — mixed private/public ownership. Pre-blackout it operated with similar regularity to Amorebieta. Post-blackout, its monthly dispatch falls steadily, displaced from Operación Reforzada’s regime.

This is very different from the north-interior corridor pattern where all plants win (Arrubal + Castejón + Escatrón). In Vizcaya there’s reshuffle: REE chose Amorebieta over BBE. Why?

Hypotheses:

1. Technical availability: BBE may have been in maintenance or had operational restrictions during the critical period (May-September 2025) that Amorebieta didn’t have
2. Commercial strategy: Axpo, as a specialist market representative, bids aggressively to maintain continuous dispatch. Gunvor/EVE, as mixed owners without a specialized Spanish trading desk, may bid less optimally
3. Technical unit characteristics: ramp rates, efficiency, age — the newer or more efficient CCGT wins when other variables equalize

Without access to the two plants’ internal operational data, we can’t close the question. But the contrast leaves one clear conclusion: in Vizcaya, unlike the north-interior corridor, the owner/operator matters.

What this tells us about the next profile

So far the three profiles show three different patterns:

1. Arrubal / ContourGlobal: hibernation → base (north-interior corridor, pure geography)
2. Castejón / TotalEnergies: rare peaker → base (north-interior corridor, geography + operator scale)
3. Amorebieta / Castleton (via Axpo): active → 5-month extreme saturation → active (Vizcaya, owner-operator matters more than region)

Each profile illuminates a different mechanism of the post-blackout reshuffle. In the next and final post in the series we connect the pieces: the general thesis on how geography and owner combine to decide who wins Operación Reforzada.

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