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September 18, 2025 Clean Horizon is pleased to announce the latest update of the Storage Index, now expanded to include the Baltic countries.
You can find the updated Storage Index here.
Our expert team provides fresh insights into the performance of battery energy storage across Europe.
Since the opening of the ancillary service markets until August 2025, market prices have been soaring in the Baltics. On average, ancillary service capacity reservation prices in the Baltics are 2 to 8 times higher than in Finland. Several times this year, prices reached all-time highs, hitting the €4,000/MW/h cap in mFRR. For a 2h battery, yearly revenues in the Baltics ranged between €700k/MW/year and €3,500k/MW/year. In Estonia, batteries achieved some of the highest revenues in Europe, with April 2025 setting a record: annualised revenues reached €5.3 million per installed MW, driven by exceptionally high mFRR reservation prices.
Revenues dropped by approximately 35% in August, reaching 220 kEUR/MW/y for 2-hour configuration. This decline is mainly driven by a decrease in aFRR capacity prices, which fell by a similar margin last month. At the same time, aFRR energy (PICASSO) reached its lowest-ever spreads. Both factors are the main contributors to this sharp drop in revenue.
With the increase in reservation prices for FCR and mFRR, short-duration batteries were able to boost their revenues in August 2025 compared to July. However, the decrease in successive spreads on aFRR led to lower revenues for 4-hour batteries during this period.
The completion of works on the 400 kV line on August 10 allowed batteries to benefit from more attractive prices on FCR N/D and aFRR. As a result, revenues generated by batteries in DK2 increased in August compared to July.
In August, BESS revenues surged to their highest level in six months, driven mainly by rising capacity reservation prices. While aFRR energy and balancing spreads fell by 5% and 42% respectively, and the day-ahead spread averaged 108 €/MWh, reservation prices rose by 58% on average. Notably, FCR-N prices nearly doubled to 28 €/MW/h, while FCR-D down prices more than tripled, reaching 24 €/MW/h.
In August, BESS revenues in France declined slightly compared to July, mainly due to a small decrease in aFRR capacity reservation prices. Meanwhile, Day-Ahead market spreads continued to rise.
In August, revenues from 2-hour BESS recorded the strongest increase, with 9.5% more revenue than in the previous month. They benefited from a 20% increase in the average reservation price of the aFRR DOWN and a 25% increase in the daily day-ahead spread, both due to high solar production. Since 1-hour BESS are limited to take advantage of these two opportunities, their revenues increased by only 1%, while revenues from 4-hour BESS increased by 3%, with a smaller marginal gain.
MB spreads are better than MSD and DA; however, the gap has been reducing over the last 3 months, but the MB spreads are reducing as well. A substantial proportion of the revenues are from intraday. Overall, the 1h index has reduced by 24% and 2h by 9%, while the 4h index stays at a relatively same level as last month.
Revenues are still increasing during the summer: high PV production brings great volatility on the DA and high prices on ancillary services.
In August, the BESS revenues have increased by 12% on average for all durations. This revenue augmentation is mainly explained by the increase in the aFRR reservation down prices by more than 28%. On the other hand, the aFRR activation spreads have decreased by 7% and the DA spreads by 2%. Finally, the balancing mechanism spread has dropped by 4%.
The Sweden storage index remains at the same levels as July. However, the composition of the revenues has changed. There has been a 50% increase in FCR-N prices, and a 23% decrease in mFRR capacity reservation prices. This has translated to a drop in the share of mFRR capacity reservation from 89% in July to 72% and an increase of FCR-N revenues from 6% to 20% in August.
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