November 2025

251101

ENERGY CHRONICLE



According to the Federal Network Agency, German electricity grid operators received a total of 9,710 applications for grid connections for battery storage systems last year, adding up to a total capacity of 661.2 gigawatts. Of these, 4,261 with 326.5 gigawatts were still under review. A total of 3,818 applications with a capacity of 46.5 gigawatts that had been received in 2004 or earlier were approved. If all of these approved projects were actually implemented, this would result in a twentyfold increase in the currently installed battery storage capacity of 2.3 gigawatts.

“Storage tsunami” floods electricity grid operators

German electricity grid operators are facing a veritable tsunami of storage connection requests”. This is how the East German transmission system operator 50Hertz described the situation when it published a statement on the “ramp-up of large-scale battery storage” a few months ago. At that time, it estimated its own intake of project requests at 100 gigawatts (GW). By mid-November, this had risen to 150 GW. By way of comparison, the total output of all power plants installed in Germany for public electricity supply is around 250 GW.

And 50Hertz is only one of four transmission system operators. Amprion, TenneT, and TransnetBW are not quite as overwhelmed with relevant inquiries, but the total would at least double if these were added. This total capacity alone would be enough to cover Germany's entire electricity needs and more from battery storage until capacities are exhausted.

In the distribution networks, there were a total of 672.4 gigawatts of power requested last year.

In addition, below the transmission level (220 and 380 kV), there are many more applicants in the distribution networks who want to connect a battery storage system to medium voltage (more than 1 kV) or high voltage (100 kV). According to a survey published by the Federal Network Agency on November 12, distribution network operators received a total of 9,212 requests with a capacity of 493.6 GW last year (unfortunately, more recent data is not available), of which 1,568 with 260.8 GW were still pending, 3,854 with 198.4 GW were under review, and 3,790 with 34.4 GW had been approved. Transmission system operators received 498 requests totaling 167.6 GW, of which 63 (27.4 GW) were still pending, 407 (128.1 GW) were under review, and 28 (12.1 GW) had been approved (see Charts).

The implementation of all applications approved in 2024 would increase battery storage capacity twentyfold.

According to this announcement by the Federal Network Agency, the market master data register currently lists 921 battery storage facilities with a connection from the medium-voltage level upwards. These systems have a net nominal capacity of around 2.3 GW and a storage capacity of around 3.2 GWh. If only the 3,818 projects approved in 2024 with 46.5 GW were to be implemented, this would correspond to “a multiplication of the current stock,” as the Federal Network Agency notes. Or, to put it in concrete terms: the number of plants would increase from 921 to 4,739, i.e., fivefold, and their capacity from 2.3 GW to 48.8 GW, i.e., more than twentyfold.

Many project developers submit the same application for several locations

In its paper on the “ramp-up of large-scale battery storage,” 50Hertz cites the following reasons for the boom:

At the same time, the rapid increase in battery connection applications to the transmission grid is due to the fact that the business model of the operators of such plants – i.e., the exploitation of short-term price fluctuations on the electricity market – is becoming less lucrative with each newly connected battery. The earlier a storage facility is connected, the more it can benefit from price differences. The resulting competition for the earliest possible grid connection is driving up land prices at potential storage sites, with the result that real estate owners and speculators who have no project experience in the energy sector are also submitting their own applications. Since there are currently no costs associated with a connection request, many project developers are also submitting the same application for several locations in order to increase their chances of being awarded a contract somewhere.

The current grid connection procedure urgently needs to be reformed

The East German transmission system operator considers a fundamental reform of the grid connection procedure to be necessary, as also called for by the Bundestag in a resolution on November 13 (251102). In the case of multiple applications for the same grid connection point, prioritization should no longer be based on a “first come, first served” basis, but on the proven maturity of the project. Above all, the entire Power Plant Grid Connection Ordinance (KraftNAV) should no longer be applied to battery storage systems – a demand that the Bundesrat also supports and wanted to include in the recently adopted amendment to the Energy Industry Act (EnWG). Although this did not happen, the state representatives may have provided the impetus for the aforementioned resolution, which calls on the federal government to fundamentally reform the grid connection procedure.

At the time, the KraftNAV was intended for ten applications for power plant connections per year.

The KraftNAV dates back to 2007 and regulates the connection of generation plants from 100 MW and 110 kV. It was tailored exclusively to power plants. At that time, grid-connected battery storage systems were practically non-existent, apart from a small number of home storage systems that were not subject to approval and did not feed their negligible amounts of electricity back into the grid. It was not until seven years later that grid-connected battery storage systems appeared in the statistics for the first time, with a minimum value of 0.01 GW (see tables).

In the absence of any legal basis other than the KraftNAV, the connection applications for these few battery storage systems, which with some effort could also be classified as “generation plants,” were treated in the same way as power plants. It is possible that a false analogy was made with pumped storage power plants, as suggested by the word “storage.”

No wonder, then, that the current flood of applications is overwhelming the electricity grid operators. According to the explanatory memorandum to the law at the time, the KraftNAV was intended for around ten applications for power plant connections per year. In the case of 50Hertz, that would correspond to two to three applications per year. In fact, however, the East German transmission system operator is struggling with a flood of applications in the triple digits.

For arbitrage transactions on the electricity exchange, the pie gets smaller with every plant

Presumably, the “storage tsunami” consists of more foam than water. Common sense and basic arithmetic tell us that. Because if such a huge number of connection applications were actually approved and even only mostly realized, the operators of the plants would have to cannibalize each other and still would not be satisfied. Of course, a distinction must be made between necessary or at least “grid-friendly” plants, which always have a chance, and purely commercial projects, which are essentially only aimed at arbitrage transactions on the electricity exchange. For the latter, the pie gets smaller with every new plant. For the time being, it will be important not to simply process the flood of applications chronologically on a “first come, first served” basis, but to make a preliminary selection that separates the wheat from the chaff.

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Background


This is what the 250 MW battery storage facility at the Kupferzell substation (right) will look like when TransnetBW puts it into operation next year. However, it may only use it for so-called redispatch or as a “fully integrated grid component,” as Section 7 of the Energy Industry Act (EnwG) prohibits electricity grid operators from “owning, constructing, managing, or operating an energy storage facility.”

What was once “the world's largest battery storage facility” would be a mere dwarf today

Battery storage facilities played an important role in the early days of electricity supply. The first power plants, which were able to generate electrical energy on a large scale for the first time using the dynamo principle discovered by Werner Siemens in 1866, were still quite prone to failure and comparatively inefficient. It was therefore fortunate that the first “accumulators” came onto the market at the same time as the first local power grids. These were a further development of the long-established “galvanic cells,” which were designed according to different chemical formulas so that energy could be converted into electricity when needed. However, this only happened until the chemical energy potential was exhausted (as is still the case today with simple flashlight batteries).

With a modified design of the cells, it was now possible to make this energy conversion reversible. This meant that the accumulators could be both discharged and recharged. By connecting them to the generators of the power plants—which initially only produced direct current anyway—it was possible to bridge the still frequent power outages, at least in the short term, or to increase the power plant's output at nightfall by connecting the accumulators. In the beginning, electricity was used almost exclusively for electric lighting.

Pumped storage power plants and alternating current replaced battery storage

With the increase in consumption, power plant output, security of supply, and the networking of local structures, battery storage played an increasingly minor role in the power supply. This was ensured by pumped storage power plants, which the large state and regional suppliers used to protect their respective grids against load fluctuations. In addition, battery storage systems were not compatible with alternating current, which replaced direct current across the board after World War II at the latest. Storing alternating current in accumulators and then converting it back into alternating current would have required complex converters or power converters. Despite the high costs, however, the efficiency would have been lower than with modern semiconductor-based power converters, which today enable battery storage systems to be connected to all levels of the power grid or, as “connectors,” integrate high-voltage direct current (HVDC) transmissions into the transmission grid. Due to this discrepancy between cost and benefit, battery storage systems became less and less useful for the power grid and eventually disappeared almost completely.



Until around 2014, storage power in the German power grid consisted solely of pumped storage power plants located in Germany and, to a large extent, in Austria and Luxembourg, as well as the only compressed air storage facility. Then more and more battery storage facilities were connected to the grid. These were mainly small “home storage” facilities with a capacity of up to 30 kilowatt hours, which do not require special approval but only need to be registered (red). Since 2025, the cumulative power of these home storage systems in gigawatt has even exceeded that of all pumped storage power plants. However, large storage systems with capacities of 1 MWh or more, which are taken from the grid for commercial or technical reasons and fed back into the grid at a later time, are more significant for grid operation. (See table for data on this graph)

Only Bewag operated a battery storage facility for nine years that was gigantic by the standards of the time

However, there was one notable exception: in 1986, Berlin-based Bewag commissioned a battery storage facility that was gigantic by the standards of the time. There was a specific reason for this: West Berlin had become an electricity island since 1952. As early as 1948/49, due to the Soviet blockade of land and water connections that lasted almost a year, even coal for power plants had to be flown in by airlift. Under these circumstances, it seemed sensible to build a conventional battery storage facility that was connected to the 30 kV distribution network via power converters in order to support the frequency maintenance of the island power grid.

As a precaution, it was decided to first build a test facility with a modest output of 24 kilowatts, which went into operation in 1981. After a successful three-year test phase, construction of a battery storage facility with 700 times the output began in 1984. The plant in the former Steglitz power station consisted of conventional lead-acid batteries with a total of 7,080 cells, which were connected in series in twelve strings of 590 cells each. This increased the cell voltages from around 2 volts to a total of 1,200 volts. By connecting the strings in parallel, the capacity of the battery was increased twelvefold. After conversion to alternating current and feeding into the 30-kV distribution network, this resulted in an output of 17 MW, which could be fed into the grid for twenty minutes or, at most, half an hour.

When this plant went into operation in 1986, it was undoubtedly the largest battery storage facility in Germany. It may even have been “the largest battery storage facility in the world,” as another superlative claimed. It is now a thing of the past, because after reunification and the incorporation of Berlin into the new all-German grid (941210), the battery storage facility was no longer needed and was shut down at the end of 1994 due to unprofitability.

It took until 2014 before large-scale battery storage facilities with a total capacity of 0.01 MWh appeared in the statistics for the first time.

Before a new storage boom began, two decades passed in which this sector was completely stagnant. The available current statistics, which begin in 1999 (see tables), show only gaps for all three categories of battery storage until 2004. It was not until 2005 that the minimum value of 0.01 GW or 0.01 GWh was reported for home storage (less than 30 kWh), which then remained unchanged for seven years. Nine years later, in 2014, the previous gaps for commercial storage (30 kWh to 1 MWh) and large-scale storage (more than 1 MWh) were also filled with the minimum value for the first time.

But then the power and capacity figures for all three categories increased from year to year, albeit in varying increments. In 2020, the interim result is that home storage accounts for 1.60 GWh, commercial storage for 0.13 MWh, and large-scale storage for 0.61 GWh. Together, this amounts to 2.34 GWh, representing an approximately eighty-fold increase in capacity within six years. Nevertheless, this is just 4 percent of the total 58.27 GWh of electricity storage capacity, 95 percent of which is still provided by pumped storage power plants. The remaining 1 percent is regularly accounted for by Germany's only compressed air storage power plant (100108) in the 27-year statistics.

 


When compared with the previous chart, the difference between the measured variables “power” (in gigawatts) and “capacity” (in gigawatt hours) becomes clear: although home storage systems (red) now have a greater total power output than pumped storage power plants, they are still far from reaching their capacity. So far, they have played no role in grid control. However, this could change if one day home storage systems, including the capacities of electric cars, were combined to form large virtual storage facilities. (See table for data on this chart)

Home storage systems now have more power than all pumped storage power plants combined, but they are still a long way from matching their capacity.

Another five years later, i.e. today, battery storage systems have caught up at lightning speed. Their total output currently amounts to around 15 GW and their total storage capacity to 23 GWh. As before, the vast majority of this is accounted for by home storage systems. Their total output has risen from 0.84 to 11.91 GW since 2020, with capacity increasing from 1.60 to 18.75 GWh. This means that they even have 2 GW more installed capacity than all pumped storage power plants (9.90 GW). In terms of capacity, however, they are still literally nowhere near matching them, as pumped storage power plants have a total of 54.58 GWh of stored kinetic energy, while the chemically stored energy of all battery storage systems combined only amounts to 23.16 GWh of electricity.

A look at the ENERGY CHRONICLE reveals the following projects, listed in chronological order from 2013 onwards. They illustrate not only the technical dimensions of large-scale and home storage systems, but also the different purposes for which they can be used. It also becomes clear who offers, operates, or finances such storage systems:

Commercial operation is generally in harmony with grid requirements

The latter project in particular, in which foreign investors are financing a 100 MW battery storage facility in the Bavarian Fichtelgebirge mountains, is a clear example of how grid considerations and requirements often play only a secondary role in the construction of such large-scale storage facilities. Of course, the project should have a grid-related benefit that can be used as an argument for it to be approved in the first place. However, the main motive of the operators is usually purely financial interest in exploiting the daily fluctuations in the stock market price of electricity for arbitrage transactions: The aim is to buy electricity as cheaply as possible when the exchange price is low or even negative, and then sell it back on the exchange when the spot market price is as high as possible. This does not rule out the possibility of agreeing to provide a specific grid service, such as the provision of balancing energy.

Such storage facilities are not primarily used to balance load fluctuations, but to generate profits. Nevertheless, the grid effect is usually similar in practice, because the price signals on the spot market that trigger it are themselves caused by the short-term foreseeable shortage or surplus of available power plant capacity. However, there are also situations in which the purely commercial operation of a storage facility can run counter to grid requirements.

Electricity grid operators are not permitted to own battery storage facilities themselves


Larger solar parks are now generally equipped with battery storage facilities in order to be able to feed electricity into the grid and generate income from it in a more flexible manner. In this photo, a crane is transporting one of the typical containers in which the battery cells are housed to its new location, where two other modules of this type are already in place.

Photos (2): EnBW

However, Section 7 of the Energy Industry Act (EnwG) prohibits electricity grid operators from “owning, constructing, managing, or operating an energy storage facility.” This applies in particular to transmission system operators. This is due to the fundamental separation of ownership of electricity generation from the grid and distribution sector, which was introduced with the liberalization of the energy market. The only exceptions to this are energy suppliers with up to 100,000 customers, i.e., small to medium-sized municipal utilities.

Larger grid operators can therefore only put out a tender for the construction of an electricity storage facility, which is then owned by a third party and operated by that party in accordance with the agreements made in advance. In November, Nuremberg-based N-ERGIE Netz GmbH launched a tender for a “grid-friendly” battery storage facility with a capacity of 20 MW and a capacity of 80 megawatt hours in order to make its approximately 29,000-kilometer-long electricity distribution network, which supplies about one-tenth of Bavaria, more flexible. However, the investor must commit in their application to align the charging and discharging of the storage facility with the technical requirements of the grid.

Exemption for storage facilities that are a “fully integrated grid component”

In addition, since 2021, Section 11b of the EnWG has offered larger grid operators the opportunity to become owners and operators of electricity storage facilities if these facilities are a “fully integrated grid component” that is necessary for grid operation and if no third party can be found to own them. Probably the best-known example is the “grid booster” that EnBW subsidiary TransnetBW is currently implementing at the Kupferzell grid node and which is scheduled to go into operation next year. This storage facility can provide 250 megawatts of power in a matter of seconds, helping to overcome frequent grid bottlenecks via “resdipatch.” However, it may only be used for this purpose.

The situation is different for a battery storage facility with an output of 100 megawatts and a capacity of 100 megawatt hours, which EnBW Kraftwerke is currently building in Marbach. As a power plant operator, the group has a free hand in how it uses this storage facility, which will be connected to the TransnetBW transmission grid. Above all, it can store the output from solar or wind farms in order to feed it into the grid at the most financially or technically favorable time (although most solar parks are already equipped with battery storage systems).

In Philippsburg, EnBW is even planning a battery storage facility with 400 MW and 800 MWh

When EnBW announced the project in Marbach a year ago, it spoke of “by far the largest battery storage facility in EnBW's generation sector to date” – a statement that deliberately ignored TransnetBW's grid booster in Kupferzell, which is more than twice as large (241108). In the meantime, however, it has announced another project that surpasses both of these: On the site of the former Philippsburg nuclear power plant (200508), where the A-Nord / Ultranet “electricity highway” (231001) from northern Germany will end, it plans to build a battery storage facility with a capacity of 400 megawatts and a capacity of 800 megawatt hours. “The large-scale project is to be realized without government funding,” the announcement said. “In addition to the proceeds from the sale of electricity, the storage facility is to be financed by offering grid services.”

Compared to the 14 megawatt hours available to the battery storage facility of Berlin-based Bewag, which was the largest in Germany at the time and even considered the largest in the world, this is 57 times more capacity. Seen in this light, the giant Berlin facility shrinks to a dwarf in retrospect. But it still belongs in the “large storage” category, which starts at 1 MWh.

See also: