Enervis Battery Storage Index: Significant decline in revenues in July
Source：pv magazine
Since the first quarter of 2025, at Enervis, we have been publishing a monthly Battery Storage Index based on historical market data. The first publication of the index was presented in an initial article in March 2025. The index illustrates revenue opportunities for battery storage systems 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 July 2025
In July 2025, achievable revenues recorded a significant decline compared to June, falling to around €12,100 per megawatt. This corresponds to a decrease of 32% compared to June 2025 and 24% compared to July 2024. The decline highlights the strong link between PV generation, market volatility, and potential revenues for battery storage. After a sharp increase in PV generation between April and June, July saw a marked reduction due to very low solar irradiation. As a result, Day-Ahead and Intraday spreads contracted significantly, while FCR and aFRR prices also declined, factors that jointly contributed to the reduction in achievable revenues. July 2025 was exceptionally weak in terms of solar irradiation, whereas the improved sunshine conditions in August are expected to lead to a renewed increase in revenues.
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 €151,000 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.
The achievable revenues for the full year 2025 continue to be based on our Current Efforts Scenario Q3/2025; no update of the scenario was carried out this month. The projected revenues currently amount to €151,600 per megawatt per year.
The projected revenues for 2025, at €151,600 per megawatt per year, are slightly above the average achievable revenues of the past twelve months, but remain within the same order of magnitude as illustrated in our Battery Storage Index. The storage parameters have been 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 Q3/2025.