On Thursday 7 May 2026, a fire broke out at an external data centre in Almere. It hosted the Crowd Balancing Platform (CBP), the system that the Dutch transmission system operator, TenneT, uses to connect aggregated assets to its aFRR market. The CBP stayed offline until the morning of Friday 15 May.

For nine delivery days, providers connected through the CBP, BESS among them, could not offer automatic frequency restoration reserve (aFRR). From 8 to 16 May, upward plus downward aFRR capacity cost TenneT €234/MW/h on average, more than 5 times the €43/MW/h of the 9 days before.

Key takeaways

• The fire took aFRR back to the days when thermal power plants set the price: in the daily product, TenneT paid €123/MW/h up plus down, just above a gas plant’s €110/MW/h break-even price.
• The CBP outage reminds us what flexible assets like BESS save on balancing: since July 2024, TenneT paid €419 million less for aFRR capacity than if gas plants had kept setting the price.
• A BESS that relies on the CBP earned 31% to 37% less in May than Modo’s Dutch benchmark shows. Treat the outage as a one-off in any investment case.

How did the fire cut the available aFRR offer?

The fire cut only the CBP. From then on, only providers with their own link to TenneT, a remote terminal unit (RTU) on a leased line or a TenneT private connection, could receive activation signals and so sell aFRR. TenneT does not publish how much aFRR capacity is offered, but the aFRR energy bid ladder gives an indication. The chart pairs each delivery day with the ladder of the day before, when its capacity auction ran. The offered upward aFRR energy bids fell by 40%, from about 800 MW in the nine days before to 480 MW, while TenneT still needed at least 380 MW.