December 2025 Storage Index is out!

Clean Horizon delivers the latest snapshot of BESS performance across Europe – clear, concise, and focused on the trends that matter most to developers, investors, and policymakers.

Below is our latest snapshot of regional insights:

Belgium:

December recorded the lowest revenue levels since January 2023. Revenues ranged between 80 k€ /MW/year and 100 k€ /MW/year for 2-hour and 4-hour configuration respectively, mainly driven down by low aFRR capacity prices, which averaged 2 €/MW/h to 6 €/MW/h throughout the month. Despite the low reservation prices, aFRR and imbalance spreads remained relatively attractive, at around €150/MWh.

Danemark:

• DK1: Despite lower volatility in the energy markets (DA and aFRR energy), aFRR capacity prices increased on the UP side during December. This increase offsets the drop also observed in FCR reservation prices, which explains the slight rise in battery revenues in DK1 over the month.
• DK2: Unlike DK1, aFRR reservation prices fell in DK2, along with energy-market volatility. As a result, battery revenues decreased in DK2 in December.

Estonia:

Once again, revenues for BESS declined, falling by 37% between November and December for a 2-hour BESS. This decrease was mainly driven by a sharp drop in FCR capacity prices, which fell from 64€/MW/h to just 15€/MW/h. In addition, day-ahead average spreads declined significantly (-36%). Day-ahead prices were pushed down by very strong wind generation in the region, combined with low-cost imports from Finland.

Finland:

In December, BESS revenues remained relatively stable at low levels, with only the 2-hour BESS showing a decline. This was driven by the continued drop in prices across both capacity reservation markets (averaging a 30% decrease) and energy activation markets, where spreads fell by 16% on average compared to the previous month.

France:

2-hour BESS revenues slightly dropped by 7% in December due to a decrease in aFRR reservation prices and day-ahead spreads compared to November, with aFRR Down decreasing by 25%, aFRR Up by 20%, and day-ahead spreads by 15%. Revenues for 1-hour and 4-hour BESS remained stable.

Germany:

Revenues in December were stable compared to the previous month. Spreads on the aFRR activation market and the day-ahead narrowed slightly, resulting in a stronger decline in revenues for 4-hour BESS (-3,7%) than for 1-hour and 2-hour BESS (-1.2% and -2.5% respectively). Over the whole 2025 year, BESS of all durations have experienced an increase in revenues compared to year 2024, driven by higher aFRR reservation prices and higher spreads on the day-ahead market. The matters foremost benefited 2-hour and 4-hour BESSs, whose annual revenues increased by 17%.

Italy:

In general, MB market has better spreads than DA and MSD. This month however, the spread on MB has dropped by 98% and this has had a direct impact on the index which has dropped by ~35% this month for the 4h index.

Latvia:

Revenues for BESS declined sharply for the fifth consecutive month, falling by 40% between November and December for a 2-hour BESS. This decrease was mainly driven by a sharp drop in FCR capacity prices, which fell from 70€/MW/h to just 14€/MW/h. In addition, day-ahead average spreads declined significantly (-36%). Day-ahead prices decreased due to high wind power generation and lower electricity consumption.

Lithuania:

Once again, revenues for BESS declined for the fifth consecutive month, falling by 32% between November and December for a 2-hour BESS. This decrease was mainly driven by a sharp drop in FCR capacity prices, which fell from 70€/MW/h to just 14€/MW/h. In addition, day-ahead average spreads declined significantly (-36%). Day-ahead prices decreased due to high wind power generation, which covered around 42% of the country’s electricity demand.

Poland:

Capacity reservation prices remained high in December, offering great revenues for BESS. However, DA spread reached the 2025 record low (around 73€/MWh) this month, a huge drop compared to the 150€/MWh average spread in 2025. This is the result of an abnormally low PV production and a high wind production in the evening. Overall, there has been a light decrease in the revenues for BESS in December, but opportunities stay high in Poland.

Spain:

In December, the BESS revenues have decreased by 29% on average for all durations. This revenue diminution is mainly driven by the fall of aFRR reservation up and down prices by 24% and 31%, respectively. The aFRR spread has also decreased by 40% while the mFRR spread by 24%. Finally, the DA spread has dropped by 36% in December in comparison to November.

Sweden:

There is a nearly 50% drop in the Swedish index for the month of December. This is mainly due to all capacity reservation prices dropping 40-50%. This is the first month since Feb 2025 in which the mFRR capacity prices are no longer the highest, dropping slightly below FCR-N and also reaching their lowest level in 2025. The initial shock of prices post the transition to 15min has passed as seen by the steady decline in prices. Svenska kraftnat also notes an increase in prequalified volumes especially batteries and wind which has also had an impact. Prequalified energy storage in mFRR specifically has increase from 120 MW in Jan 2025 to ~900MW in September.

You can find the updated Storage Index here.

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