€766
per MW per day: what a four-hour battery would have earned in September 2026.
Analysis · battery storage in Spain
What a four-hour battery earns in Spain, month by month.
I ran Spain's OMIE day-ahead prices from January 2025 to September 2026 through a simple model of a four-hour battery. The result explains both why the market is excited about storage and why lenders are right to be careful.
Ignacio López Martín ·
€163
per MW per day in December 2025, the weakest month of the series.
42%
of the last twelve months' revenue (October 2025 to September 2026) came in July, August and September.
+34%
January to September 2026 against the same months of 2025: about €120,000 per MW so far in 2026.
Month by month
| Month | € per MW per day |
|---|---|
| Jan 2025 | 240 |
| Feb 2025 | 357 |
| Mar 2025 | 311 |
| Apr 2025 | 291 |
| May 2025 | 231 |
| Jun 2025 | 422 |
| Jul 2025 | 331 |
| Aug 2025 | 379 |
| Sep 2025 | 399 |
| Oct 2025 | 357 |
| Nov 2025 | 308 |
| Dec 2025 | 163 |
| Jan 2026 | 180 |
| Feb 2026 | 238 |
| Mar 2026 | 312 |
| Apr 2026 | 347 |
| May 2026 | 443 |
| Jun 2026 | 455 |
| Jul 2026 | 511 |
| Aug 2026 | 702 |
| Sep 2026 | 766 |
How to read it
It is a ceiling. The model buys in the cheapest hours and sells in the dearest ones every single day, with perfect foresight. No real battery does that.
It is seasonal. Summer spreads are wide because solar pushes midday prices down and gas sets the evening peak. In December the spread almost closes.
It will narrow. Night prices in Spain are set by gas, and gas will not stay expensive forever. Every new battery also narrows the spread it lives on.
What gets financed is a floor: contracts shaped like demand, batteries at plants that already have a grid connection, and a capacity market that moves from the official gazette to actual auctions.
Method
OMIE marginal day-ahead price for Spain (marginalpdbc files): hourly until September 2025 and quarter-hourly from October 2025. A four-hour battery, one full cycle a day, 87% round-trip efficiency, charging in the cheapest hours and discharging in the most expensive hours of each day with perfect foresight. Excludes ancillary services, capacity payments, intraday trading, degradation, grid charges and taxes. Monthly figure = average daily revenue per MW of power.
Published in: El Español-Invertia, 15 October 2026 (op-ed, in Spanish)