German battery storage developers are challenging a core cost assumption: if grid operators curtail storage access through flexible connection agreements, the hefty Baukostenzuschuss (BKZ) fee must fall proportionally. Kyon Energy’s regulatory lead Marie-Sophie Braun has formalised this demand, arguing that restricted grid access without commensurate fee reductions undermines the business case for the very assets Germany needs to integrate renewables. The outcome will reshape project economics across the 15 GW-plus pipeline and set a precedent for how Europe’s largest market balances grid congestion against storage deployment.
How flexible connection agreements and BKZ fees collide in German grid practice
Germany’s distribution and transmission operators have accelerated the use of flexible connection agreements – known locally as Netzanschluss mit Beschränkung or FCA-style arrangements – to connect batteries faster without waiting for physical grid reinforcement. Under these deals, a storage asset receives permission to inject or withdraw power only up to a dynamic limit that the grid operator can reduce in real time during congestion. The trade-off is clear: the developer gets a connection date years earlier, but accepts curtailment risk that can slash revenues from arbitrage, frequency response, and capacity markets.
The BKZ, by contrast, is a one-off construction-cost contribution levied on the connecting party to cover the grid operator’s expense for transformers, switchgear, and cable upgrades triggered by the new connection. Fees typically range from €80 to €300 per kW of contracted capacity depending on voltage level and regional reinforcement needs. For a 100 MW / 200 MWh project, the BKZ alone can exceed €15 million – often the single largest capital-expenditure line after the battery hardware itself. Crucially, the fee is calculated on the maximum contracted capacity, not the expected utilisation under a flexible agreement.
Until now, regulators and grid operators have treated the BKZ as a sunk cost tied to physical infrastructure, arguing that the assets are built regardless of how often the storage unit actually uses them. Developers counter that the infrastructure is sized for a capacity the asset is contractually barred from using during congestion hours – which in some northern German nodes now exceed 1,000 hours per year. The Bundesnetzagentur’s 2023 monitoring report showed average curtailment rates for flexible connections of 12-18 % in Schleswig-Holstein and Lower Saxony, with peaks above 30 % on windy winter weekends. That points to a structural mismatch: developers pay for firm capacity but receive a product that behaves more like an interruptible one.
Why this dispute reverberates beyond Germany’s borders
The German standoff mirrors a wider European tension between accelerated connection timelines and cost-reflective pricing. In Great Britain, National Grid ESO’s “Connect and Manage” reforms have similarly decoupled connection dates from reinforcement, but the UK uses a different cost-allocation model – the Transmission Network Use of System (TNUoS) charges – where storage already benefits from reduced demand residuals. The Netherlands’ TenneT has piloted “conditional firm” connections with explicit curtailment caps and a proportional reduction in connection fees, creating a template the German regulator could adopt. If the Bundesnetzagentur endorses a BKZ haircut for flexible agreements, it would establish the first major continental precedent linking connection fees directly to utilisation risk, potentially influencing the EU’s ongoing Network Code on Demand Connection revision.
Quantitatively, a 20 % BKZ reduction on a 100 MW project at €200/kW saves €4 million upfront – improving the project’s internal rate of return by roughly 150-200 basis points under current German wholesale and ancillary-service price assumptions. That magnitude can flip a marginal project into an investable one, especially for merchant revenue stacks that lack long-term offtake contracts. Conversely, if the fee stays flat, developers will increasingly site projects in southern grid zones where congestion is lower but renewable curtailment value is also smaller, undermining the system-wide benefit of placing storage where wind oversupply is greatest.
Who this affects
- Storage developers (e.g., Kyon, Fluence, BayWa r.e.): Direct hit to capex models; a BKZ reduction rule would unlock northern sites currently pencilled as uneconomic and accelerate final investment decisions on 3-5 GW of near-term pipeline.
- Distribution system operators (e.g., Schleswig-Holstein Netz, Bayernwerk): Revenue certainty from BKZ collections declines if fees become utilisation-linked; they must justify reinforcement budgets to regulators with lower upfront income.
- Transmission system operators (50Hertz, TenneT DE, Amprion, TransnetBW): Precedent could extend to TSO-level connection charges, affecting hybrid offshore wind-storage projects and cross-border interconnectors.
- Institutional investors and infrastructure funds: Due-diligence checklists must now stress-test BKZ sensitivity; projects with flexible connections need explicit curtailment scenarios in base-case financial models.
- Policy analysts and Bundesnetzagentur staff: Must define “commensurate reduction” – a percentage haircut, a curtailment-hours trigger, or a dynamic fee – and embed it in the next Grid Fee Ordinance (StromNEV) amendment cycle.
What to watch next
- Bundesnetzagentur consultation response (Q3 2025): The regulator’s formal position on BKZ proportionality for flexible connections, expected after the current stakeholder feedback window closes.
- First court or arbitration ruling: A developer challenge under §118 EnWG (Energy Industry Act) could force a binding interpretation faster than legislative change.
- TSO-DSO coordination paper on “Kostenverteilung” (cost allocation): Joint working group due to publish recommendations by year-end; will signal whether fee reductions are funded by grid users or absorbed by operators.
- EU ACER opinion on Network Code Demand Connection (2026): If ACER endorses utilisation-linked fees, German implementation becomes a compliance requirement, not just a national choice.
Bottom line: The BKZ-FCA mismatch is no longer a niche regulatory detail – it is the fulcrum on which Germany’s 2030 storage target of 30-40 GW pivots. A fee structure that charges firm prices for flexible access will quietly reroute gigawatts of storage away from the congested north, exactly where the system needs them most.
Read the full report at Energy Storage News
Note: facts and figures attributed above to Energy Storage News reflect that outlet's original reporting. Broader context, cross-sector connections, and forward-looking scenarios reflect independent analysis by our editorial team.
About this article: Drafted by Energy Ai with AI-assisted research and writing based on public reporting, then reviewed under our editorial process before publication.
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