Spain's intraday continuous market (ICM) traded approximately 1.6 TWh in Q4 2025. Germany's equivalent market traded 30 TWh over the same period, roughly 19x more.

For BESS developers entering the Iberian market, the question is whether the continuous market alone can sustain algorithmic trading strategies. Spain's ICM offers price spreads against the day-ahead market reaching ±50 €/MWh. The opportunity exists. However, low volumes and small trade sizes make scaling difficult.

In Germany, renewable portfolios generate enough continuous market activity for batteries to capture value algorithmically. In Spain, limited ICM liquidity will force batteries to optimise across the day-ahead market, secondary (aFRR), tertiary (mFRR), and technical constraints. Cross-market optimisation, which can itself be algorithmic, will form the foundation of Spain's battery business model.

Key takeaways

• Most individual ICM transactions in Spain fall below 1 MWh, constraining execution at scale for batteries seeking to trade larger volumes.
• Intraday price spreads relative to the day-ahead market reached ±50 €/MWh in Spain during November 2025, confirming the existence of arbitrage opportunities.
• Germany executes 15 to 22 million ICM trades per month versus Spain's 1 to 2 million, reflecting years of renewable portfolio activity concentrated in the continuous channel.

Why do Spain's ICM prices diverge so far from day-ahead?

Spain operated six local intraday auction sessions for over a decade. In June 2024, the Comisión Nacional de los Mercados y la Competencia (CNMC) replaced them with three pan-European Intraday Auctions (IDAs), running at 15:00 (D-1), 22:00 (D-1), and 10:00 (D). The continuous market, which launched in June 2018 through the Single Intraday Coupling (SIDC), runs in parallel. However, Spanish participants concentrated their intraday activity in the auctions.

Intraday trades during the last week of November exhibited significant downward volatility. The day-ahead reference price was higher than the intraday continuous market price for several days, which ended up trading at.

Spread dispersion is widest when trades occur more than 12 hours before delivery, when uncertainty about generation and demand is highest. As delivery approaches, spreads narrow but remain meaningful.

What do trade sizes and origin zones reveal about Spain's ICM?

In Spain's ICM, around 1.6 TWh of Q4 2025 volume originated from Spanish market zones. Foreign zones contributed 0.78 TWh. Portugal accounted for approximately 0.2 TWh. Both bars include cross-Iberian trades between Spain and Portugal.