Battery Storage and the 2,500-Hour Rule – What Needs to Be Considered?
Jul 11, 2025

The 2,500-Hour Rule in electricity is a special tariff regulation for grid fees primarily affecting larger electricity consumers. It defines a threshold at 2,500 annual usage hours, beyond which the calculation of grid costs changes significantly. Below, we explain what this rule is about and why it exists. We then examine how installing a battery storage system (e.g., for peak shaving or optimizing self-consumption) can affect this rule, including a scenario with a 500,000 kWh annual consumption and around 200 kW peak load. Finally, we highlight criticisms of the rule and how the grid fee system might change in the future.
What does the 2,500-Hour Rule state and why does it exist?
Usage hours indicate how many hours per year a consumer would theoretically fully utilize their maximum power. Mathematically, this is the annual energy usage (kWh) divided by the highest drawn power (kW). This ratio serves as an indicator of the consistency of grid usage: A business with a constant load has high usage hours, whereas a business with pronounced peak loads and otherwise low consumption shows low usage hours.

The graphic shows annual electricity costs depending on peak load with a constant annual consumption of 500,000 kWh. The prices correspond to a medium voltage in the Bayernwerk grid. At the 2,500-hour threshold, the tariff structure changes: Below it, a high energy price and low power price apply; above it, the opposite is true. This leads to a noticeable kink in the slope of the cost curve – even if the absolute cost jump remains minimal (here: €8). Therefore, optimization around this point is economically sensitive.
The 2,500-Hour Rule forms a kink point in the grid fee calculation. Up to 2,500 usage hours, a relatively low power price (€/kW) and a high energy price (ct/kWh) apply; beyond 2,500 hours, the relationship reverses – a high power price and a low energy price apply. In other words:
Less than 2,500 h/a: The grid operator classifies the customer as a low user. The annual power component (for the maximum kW peak) is cheaper, but the energy component (for each kWh consumed) is more expensive. This model therefore favors customers with irregular consumption and occasional peaks – they pay relatively little for the provision of connection capacity but a lot per consumed kilowatt-hour.
More than 2,500 h/a: The customer is considered a high user with a consistent load. Here, a high power price is due, while the energy price per kWh decreases. A consistent high electricity supply is thus rewarded through favorable energy prices; however, more must be paid for the constantly used grid capacity (high kW fee).
This division ensures that at exactly 2,500 hours, both tariff variants result in approximately equally high grid fees. The threshold of 2,500 hours was deliberately set in the German Electricity Grid Fee Ordinance (StromNEV), based on experience, to achieve a cost-sharing based on causation [1]. Grid operators structure their charges with four price components: energy price and power price each for <2,500 hours and for >2,500 hours. Small consumers with a standard load profile (without recording load measurement) often pay flat energy prices, undisturbed by this. However, for larger consumers with load metering (RLM customers), this 2,500-hour system automatically applies in most grid areas.
Why does this rule exist? The goal behind it is the causation-based distribution of grid costs and setting incentives for more efficient grid usage. Electricity grids have high fixed costs, especially to cover peak loads. Consumers with strongly fluctuating or irregular consumption burden the grid with high peaks and long phases of low usage. Therefore, they should contribute more to the costs by paying higher energy prices. In contrast, consistent consumers are relieved – those who use the grid more continuously are given cheaper kWh prices but pay a higher base price for the provided capacity. Overall, this regulation is intended to prevent peak load causers from getting away too cheaply at the expense of the general public, instead rewarding grid stability and consistent utilization.
Batteries, Peak Shaving, and the Impact on the 2,500h Rule
Batteries can significantly influence a company's load profile – particularly through peak shaving and self-consumption optimization. This results in a double effect on usage hours:
Peak shaving increases usage duration: If a storage unit buffers peak loads, the maximum grid import power (kW) decreases. The annual consumption from the grid remains nearly the same (apart from storage losses), so the quotient consumption/peak increases. High peak loads reduce usage duration, and their buffering increases it accordingly. A company that previously had, for example, 2,400 hours of usage duration could possibly reach >2,500 hours through sufficiently large peak shaving. This would shift it into the category with higher power price and lower energy price.
Self-consumption optimization reduces usage duration: If less load is drawn from the grid by charging the battery instead of PV feed-in, the annual work (kWh) decreases and thereby also the usage hours.
Note: The 2,500h rule can have unwanted effects on the economic efficiency of a battery. One needs to analyze precisely, into which category one falls due to the storage and how the tariff structure changes:
If a company was just below 2,500 hours, thus previously having a low power price and high energy price, peak shaving can raise it over the threshold. Then the power costs abruptly increase and the energy prices decrease. Without limiting the usage hours, e.g., installing a battery that significantly reduces the peak load might increase the usage hours from ~2,400 to perhaps 3,300 – grid fees would be recalculated and could even rise. In our example (500,000 kWh, originally ~205 kW peak), the operation paid about €28,000 in grid fees (as calculated above). Suppose the storage reduces the peak to 150 kW (usage duration ~3,333 hours). Then the expensive power price tariff applies: even if the energy price drops significantly, the high power price could nullify the savings. The savings in grid fees through the storage in this case would be low – or in the worst case, negative, if the high base fee results in higher costs than the savings from reduced kWh costs.
Therefore, care is often taken in practice to not unfavorably exceed the 2,500-hour threshold. One could, for example, control the storage in such a way that the peak load is reduced, but not too drastically – so that the usage hours remain just below 2,500. It is preferable to retain a small residual peak load and remain in the “cheaper” tariff (with low power price) rather than completely smoothing out and falling into the expensive power price. In other words: A certain level of peak shaving can be worthwhile, but too much smoothing alters the cost balance. This optimization requires careful pre-simulation of the cost structure as, for example, provided by Lumera.
Summary: A battery can optimize grid fees by reducing peak loads – but the 2,500-hour effect needs to be considered. For project developers of batteries in commerce and industry, this means: Before installation, both tariff states should be calculated. It is crucial to determine whether the storage moves the company into a different fee category and whether it ultimately saves costs or incurs additional costs.
Criticism of the 2,500h Rule and Future Changes
The 2,500-hour rule is justified from a historical perspective but is also critiqued today. Critics particularly point out:
Inhibition of flexibility: The rigid separation between energy price and power price rewards a consistent power supply but penalizes flexible consumers. In the era of energy transition, it would be desirable for industry and commerce to flexibly adapt their consumption to the electricity supply from renewable energies.
Rigid thresholds: Fixed limits (like 2,500 hours or also 7,000 hours for other privileges) lead to abrupt cost changes when one is just below or above them. These jumps are seen as unfair and economically suboptimal because small changes in consumption behavior can lead to disproportionate tariff changes.
Regional differences and lack of realism: Grid fees vary greatly depending on the grid area, in part due to historical reasons, meaning that the same consumption at different locations can cause different costs – not always proportional to the actual grid benefit. The 2,500-hour rule itself applies everywhere, but the exact value of the energy and power prices is determined locally.
In light of these criticisms, it is foreseeable that the grid fee system – and thus also the 2,500-hour rule – will be reformed. In fact, the Federal Network Agency presented a key points paper for new industrial grid fees in July 2024. It outlines a transition from rigid to flexible incentives [2]. In the future, industry and commerce are to receive reduced grid fees when consuming more during high electricity availability and less during scarcity.
Excursion: Atypical Grid Usage and the Option for <2,500 hours
A special case arises with so-called atypical grid usage (§ 19 para. 2 sent. 1 StromNEV). Here, an end consumer whose annual peak load lies outside the high load time windows defined by the grid operator can apply for an individual grid fee. In this case, the power price is no longer calculated based on the annual peak load but only on the simultaneous load during the high load time window – and it can theoretically be as low as 0 kW for controllable systems like batteries.
Important: The usage hours are still calculated as usual – as follows:
Usage hours = Annual work (kWh) / Annual peak load (kW)
even if the actual peak load is outside the high load time window. This can make grid fee models inconsistent: A consumer with few usage hours would normally pay the high energy price even though they barely burden the grid – for instance, by charging specifically outside the critical windows.
Therefore, in such cases, the Federal Network Agency allows an option: Customers with <2,500 hours can voluntarily choose the tariff structure above the threshold – i.e., low energy price, high power price. As the power price, however, is calculated based on the (very low) simultaneous high load power, this can result in a significantly lower total fee.
In practice, the optimal decision – whether to “stay below 2,500 hours” or “choose the option” – depends on several parameters: level of annual peak load, load distribution, storage control, grid area, high load window. A suitable simulation tool like Lumera can automatically compare these options and select the economically best variant. This is the only way to ensure that battery storage operators do not inadvertently fall into an unfavorable grid fee model but instead exploit the full potential for savings.
Conclusion and Recommendations:
For project developers of battery storage in commerce/industry, this means that planning current projects must take the 2,500-hour rule into account – but one should also keep an eye on the future. Currently, it applies: Optimizing grid fees = smoothing load profile without falling into a cost trap. Companies should be informed why their storage may not deliver the hoped savings (keyword 2,500-hour threshold). At the same time, it should be pointed out that the framework conditions can change. During the transition period until then, it is even more important to exploit all savings potentials (including existing special fees according to §19 StromNEV) and, if necessary, adapt operational concepts to new rules. The 2,500-hour rule was a step towards fair cost allocation and has created incentives for energy efficiency and load management. However, with growing renewable generation and new technologies, it reaches its limits. A modernization towards more flexibility is emerging – which should ultimately benefit both grid operators and battery storage operators.
[2] https://www.bundesnetzagentur.de/SharedDocs/Pressemitteilungen/DE/2024/20240724_IndustrieNE.html
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© 2025 Lumera Energy