Enervis Battery Storage Index: Revenues climb sharply in September

Energy economics consultancy enervis has been publishing a monthly “Battery Storage Index,” based on historical market data, since the first quarter of 2025. The index illustrates revenue opportunities for battery storage systems in Germany by accounting for participation in both the intraday and balancing power markets. It provides an overview of achievable revenues for each of the past 13 months.

New revenue figures for September 2025

Achievable BESS revenues in September rose sharply to around €18,600 per megawatt. This represents a 45% increase compared to August and is 26% higher than in September 2024. Wind generation dominated the supply mix in September, while rising demand due to lower temperatures added upward pressure on power prices. Several periods of negative prices, but also hours with high prices, contributed to significantly wider price spreads. Day-ahead spreads were about 24% higher than in August. Meanwhile, aFRR capacity prices increased notably over the course of the month, while FCR prices remained largely stable. These developments created favorable market conditions from which BESS assets were able to benefit strongly throughout the month.

General trends

The monthly achievable revenues have fluctuated significantly over the past 13 months. They ranged from a low of €6,770 per megawatt per month in February 2025 to a peak of €19,100 per megawatt per month, reached in May 2025. Revenues tend to be higher during the summer months, largely due to strong PV generation combined with relatively low overall electricity demand. In addition, conventional generation capacity is typically lower during summer, partly because of scheduled maintenance and, in the case of gas-fired power plants, potentially reduced efficiency under high ambient temperatures. Wind generation availability also tends to decline in summer compared to autumn and winter. As a result, short-term fluctuations or forecast errors in PV feed-in lead to increased market volatility during these months reflected in more dynamic activity on the intraday market. On average, battery storage systems generated almost €12,600 per megawatt per month in the last twelve months, amounting to approximately €151,400 per megawatt annually.

Current Expected Revenues 2025

In line with the historical methodology, the Enervis Battery Storage Index also provides a forward-looking view of revenue expectations for the current year. Based on Enervis’ latest electricity price forecasts for the intraday and balancing power markets, the operation of a typical stand-alone battery storage system in 2025 has been modelled.

For the projected revenues in 2025, the underlying power price scenario used by Enervis was updated to the Q4/2025 scenario. Compared to the previous assumption (Q3/2025), the expected revenues in the Q4 scenario remain almost unchanged, at around €151,100 per megawatt per year, which is only about €500 lower than in Q3. The market conditions most relevant for battery storage systems (particularly day-ahead spreads and ancillary service prices) are at a similar level to those in the Q3 scenario, largely explaining the minimal deviation in expected revenues between the two scenarios.

The projected revenues for 2025, at €151,100 per megawatt per year, are nearly at the same level as the average achievable revenues over the past twelve months and remain within the same general range as presented in our Battery Storage Index. The storage parameters used in the modeling were kept unchanged.

Methodological explanation: The Enervis Battery Storage Index shows the monthly net revenues that can be achieved historically and in the future in Germany for a 1 megawatt capacity and 2 megawatt hours storage volume (2 hours) battery storage system. The storage system was modeled with a use restriction of 1.5 cycles per day, a maximal depth of discharge of 90%, a technical availability of 97% and a round-trip efficiency of 87%. The index takes into account participation in the following markets: Intraday, Frequency Containment Reserve (FCR) and automatic Frequency Restoration Reserve (aFRR). Imperfect foresight and no revenues from aFRR energy are modeled. The respective prices of the markets for the historical analysis are taken from publications of the transmission system operators and EPEX-Spot. The future outlook is based on the same modeling and parameters and prices from the current Enervis power price scenario Current Efforts Q4/2025.

Further information:

If you are interested in a more detailed analysis and the full report, you can request it here.

Authors:

Mirko Schlossarczyk – Managing Director of enervis energy advisors is an experienced energy market expert. His consulting focus is on electricity price forecasts, electricity market scenarios and the asset valuation of BESS.

Jonas Anthonioz – Consultant at the energy economics consultancy enervis energy advisors, where he is responsible for battery storage-related topics. In addition to his usual tasks in revenue assessment and profitability analysis of battery storage projects, he developed the enervis BESS Index and the associated BESS Index Report.