Since April 1, 2026, a new set of rules has applied to grid connections for large battery energy storage systems (BESS) at the transmission grid level: the maturity model process. Anyone seeking a grid connection will in future have to prove project maturity – rather than simply being early enough in the queue. What lies behind this paradigm shift, and what does it mean concretely for BESS planning?
The grid connection bottleneck: Alarming numbers
Germany's energy transition needs battery storage – and urgently. The Federal Network Agency (BNetzA) estimates the actual demand at around 80 GW of installed BESS capacity in Germany. However, the core energy market data register (MaStR) currently only contains around 2.4 GW online.
There is a huge gap between demand and reality – and the cause also lies in the grid connection process:
- 9,710 applications awaiting approval according to BNetzA monitoring (medium voltage and above)
- Behind it are 400 GW BESS capacity resp. 661 GWh planned capacity
- BDEW and the German Energy Agency even estimate 500–700 GW pending connection requests
- Approved so far: only 25 GW with 46 GWh
Why so many applications? The previous first-come, first-served principle tempts [one] to Multiple and bulk requests. Project developers secure spots without demonstrating any real intention to implement [them]. The result: hopeless applications block real projects – a Gold Rush Fever at the expense of the energy transition.
The old system: KraftNAV & the first-come, first-served principle
By the end of 2025, the Power Plant Grid Connection Ordinance access to the transmission grid after the date of application. Whoever asked earlier got served earlier – regardless of how far the project had actually progressed.
With the Amendment of the KraftNAV on December 24, 2025 it was clarified that this procedure no longer applies to battery storage systems:
| System type | Valid procedure |
| Conventional power plants ≥ 100 MW | KraftNAV |
| Renewable energy plants | EEG grid connection process |
| Battery storage systems, data centers, others | NEW: Section 17 paragraph 1 Energy Industry Act (EnWG) (maturity procedure) |
As of April 1, 2026, the new regulations apply to BESS projects maturity model process the four Transmission system operator (TSOs): 50Hertz, Amprion, TenneT, and TransnetBW. This enabled them to introduce the process even faster than Network Package 2026 provided for by Katharina Reiche.
The maturity model: First ready, first served„
Basic principle
The maturity assessment process replaces prioritization by application date with a Prioritization by project maturity. Only those who prove that their project is real and ready for implementation will receive priority in the processing order. The goal: to allocate the scarce grid connection capacities to the projects with the highest probability of realization.
An overview of the three phases
Phase 1 – Information and Application Phase (3 months)
The TSOs publish available grid connection capacities by transmission capacity and technical connection options. In this phase, petitioners can clarify open questions and have their documents checked for completeness in advance. At the end is a binding deadline for application submissions – combined with a Connection fee of 50,000 euros.
Phase 2 – Cluster study with maturity-based assessment
After the deadline, the TSOs review all applications received and evaluate the project's readiness based on four equally weighted categories (25 % each):
- Site security & approval status - e.g., signed lease or purchase agreement, existing BImSchG (Federal Immission Control Act) permit
- Technical concept – reliable planning, system sizing
- Performance of the petitioner – Financability, implementation competence
- Grid & System Benefits – Contribution to grid stability and security of supply
Within each category there are Minimum requirements (knock-out criteria) and Bonus points for advanced milestones. Example: A notarized purchase agreement earns more points than a simple reservation agreement.
Projects that meet the minimum requirements are ranked by score into a Priority list recorded. Beginning with the highest-rated projects, the TSOs then check which connections are technically and systemically possible. Finally, a System study, which evaluates the interactions between projects and the overall load on the transmission grid.
Phase 3 – Communication of Results & Grid Connection Agreement
Projects that receive a grid connection enter into a formal contract conclusion with the respective TSO. Rejected projects will not be processed further and can reapply in future procedures.
What the procedure does not (yet) solve: Criticism and open questions
The maturity model process is an important step – but not a panacea. The German Energy Storage Systems Association names essential points of criticism:
- The Federal Network Agency has not yet conclusively examined the procedure – further adjustments during operation are possible
- Battery storage continue to compete with pure consumption systems (e.g., data centers), although their system role is different
- The procedure has been considered valid so far only for the transmission system – for distribution system operators (medium and high voltage), a comparable framework is lacking
- The Federal Network Agency monitors the procedure, but has not (yet) established a standardized supervisory routine
What does the maturity assessment process mean for BESS project development?
For project developers, investors, and industrial companies with their own storage project, the maturity assessment process fundamentally shifts the success criteria:
Previously decided: The early bird gets the worm. Today decides: Those who plan the most maturely will get through.
Specifically, this means:
- Site securing prior to application submission – a notarized purchase or lease agreement is not a „nice-to-have,” but a point collector
- Technical conception must be substantive – superficial planning is not sufficient to meet minimum requirements
- Proof of financing and project expertise should be documented early
- 50,000 euro connection fee must be scheduled – a preliminary review of the application documents by the TSOs is strongly recommended
Frequently asked questions about the maturity model procedure
As of when does the maturity level process apply?
Since April 1, 2026 – the first procedure of the four TSOs was initiated in April 2026.
Does the procedure also apply to PV systems?
No. The EEG grid connection process continues to apply to renewable energy systems. The maturity assessment procedure concerns battery storage systems, data centers, and comparable facilities pursuant to Section 17 of the Energy Industry Act (EnWG).
How much does participation in the maturity level process cost?
The connection fee is 50,000 euros per application. It is a prerequisite for further processing after the deadline.
How often does the procedure take place?
This has not yet been finally settled. The TSOs will decide on the frequency and timing of further rounds of proceedings.
What happens to existing inquiries under the old KraftNAV?
Existing inquiries for battery storage systems are not automatically transferred to the new procedure. Individual clarification with the responsible TSO is recommended.
Sources: Federal Network Agency (BNetzA) monitoring survey; BDEW; German Energy Agency; Core Energy Market Data Register (MaStR); Netztransparenz.de; KraftNAV (as of December 2025); Section 17 (1) EnWG.
As of June 2026 – information without guarantee, as the procedure is still under development.