Major update to our Storage Index methodology!

In January 2025, Clean Horizon launched its Storage Index, simulating historical battery revenues for a storage project across European power markets.

As of January 2026, the methodology to compute the index has been significantly refined to better reflect real-world average battery revenues.

What has changed?

• Until January 2026: The index reflected the revenue potential of a marginal 1 MW battery, fully optimized across all accessible markets, capturing the best available marginal opportunity.
• From January 2026 onward: The index now incorporates:
  • Actual available volumes in capacity reservation and energy activation markets
  • Installed storage capacity in each country.

The methodology therefore shifts from marginal MW economics to average MW economics, capturing how revenues evolve as storage penetration increases and competition intensifies.

Additionnal enhancements

• Our computation tool behind the index (COSMOS) now models battery dispatch at a 15-minute resolution (instead of 1h), aligned with the recent shift in day-ahead market products.
• Capacity mechanism revenues have been excluded from the French index calculation.
• Portugal and Romania are now covered by the index.
• Intraday revenues are now included for all countries, based on historical transaction data in each country.

The Storage Index is calculated on a monthly basis and represents the annualised gross revenue potential of a storage asset, based on energy, capacity and ancillary service prices observed during the month.

It provides a clear view of how prevailing market conditions translate into storage revenues.
Access the latest edition of the Index.