FCA: Flexible Connection Agreements for Battery Storage in Germany

1. What is an FCA?

A flexible connection agreement (FCA) is a grid connection contract with flexible operating conditions. Instead of a classic connection offer with fully firm capacity at all times, the asset owner gets connected sooner and in exchange accepts restrictions on when and how the asset may operate. This has been legally possible since 2025 under section 17 (2b) EnWG, which covers both offtake and feed-in and is therefore the relevant basis for storage, and under section 8a EEG, which covers feed-in curtailment only and therefore applies to renewables and co-location.

The driver is the boom in grid connection requests for grid-scale batteries. At the end of Q3 2025 the four German TSOs held roughly 545 applications totalling 211 GW for grid-scale storage alone, and the BDEW estimates a further 600 GW of requests at distribution level. The need assumed in the 2037/2045 grid development plan is only 41 to 94 GW by 2035.

2. Distribution network operators at a glance

3. Transmission network operators at a glance

4. How does an FCA work in practice? The SH Netz high-voltage case

SH Netz is one of the few distribution operators to publish the actual curves behind its FCA model. They illustrate how most rule-based FCA models in Germany are structured: asymmetric between charging and discharging, because the two directions address different grid problems.

How the power band works

The power band is the permitted range between feed-in and offtake at a given moment. It is recalculated hourly from normalised curves for a reference wind farm and a utility-scale PV plant together with local weather forecasts within a 25 km radius. What counts is whichever of wind or PV output is higher in the region.

These two curves are only one variant. What governs them is the normalised output of a reference utility-scale PV plant and a reference wind farm in the region. Depending on which of the two reference plants sets the limit, and on how the battery is configured, whether standalone, oversized or hybrid, SH Netz and other operators publish further FCA variants with different thresholds and curve shapes.

The asymmetry is deliberate. Feed-in is restricted when abundant renewable generation already loads the grid, while offtake is restricted when renewable generation is scarce and charging would add load without any surplus to absorb. The two states almost never coincide. What matters in practice is that the case without dark doldrums, meaning PV or wind output at or above 10 % of rated power, is the normal case: there the battery can draw full power at any hour, no matter how much higher PV and wind run. Only the narrow window below 10 % triggers any offtake restriction at all.

Night window

Between 23:00 and 05:00 the battery may charge without restriction outside dark doldrums. Even during dark doldrums SH Netz grants a minimum offtake right of 25 % of installed capacity in that window, a concession with no equivalent on the feed-in side. In individual cases, for example where night-active industry sits nearby, the night window can be withdrawn.

Scheduling process

• –T minus 60 minutes: the binding schedule must be reported to the network operator under the redispatch process. The underlying power bands are updated hourly.
• –T minus 60 to T minus 5 minutes: short-term adjustments are possible, but where congestion is expected, meaning dark doldrums below 10 % or a feed-in peak above 50 %, only in the congestion-reducing direction. In dark doldrums that means less offtake or more feed-in, at a feed-in peak more offtake or less feed-in. In the normal case between 10 % and 50 % PV or wind, adjustments are unrestricted.
• –The operator also reserves the right to intervene automatically and temporarily in exceptional grid situations.

5. Ramp rates compared

The ramp rate, or active power gradient, limits how fast a battery may change its output, regardless of which market segment triggers the change. Unlike the power bands it is usually a single symmetric value that applies equally to charging and discharging. The chart shows how long a battery needs to move from 0 % to 100 % power under each limit.

Not shown: the Bayernwerk lower bound of 1 %/min, which would mean 100 minutes to full load, and the separate, faster exemption gradients for redispatch, FCR and aFRR.

Market analysts including Enervis estimate that a 15-minute ramp can cut a battery revenue by at least 10 %, because a meaningful share of every market interval goes into ramping rather than shifting energy.

6. Ancillary services and reactive power

In every case an online data interface between the customer installation and the network control room must be set up and tested before commissioning.

7. Key takeaways

• –FCAs have had a legal basis since 2025, through section 17 (2b) EnWG and section 8a EEG, and are now the standard route to connecting grid-scale batteries despite scarce network capacity.
• –At distribution level SH Netz, MITNETZ, Avacon, Westnetz and Bayernwerk already offer detailed, partly publicly documented FCA products. Netze BW is piloting, while E.DIS and Syna still handle FCA questions case by case or inside their technical rulebook.
• –At transmission level there is no standalone FCA product but the joint maturity process of all four TSOs, in place since April 2026. It covers both grid-charged and co-located renewable-charged storage.
• –The power bands for charging and discharging are deliberately asymmetric and generation-dependent: feed-in is throttled when PV and wind run high, offtake only inside the narrow dark-doldrums window below 10 %. Outside that window charging is always unrestricted.
• –Ramp rates, by contrast, are usually a single symmetric limit for both directions, typically 6 to 10 %/min at distribution level and 6 to 20 %/min at transmission level, and can erode revenue further.