What Does an FCA Mean for a Battery Storage System's Revenue Structure?
A Restriction Analysis by suena energy
Flexible Connection Agreements (FCAs) are increasingly becoming the standard for battery storage systems. Instead of guaranteeing fixed, unrestricted grid access, this type of agreement requires the plant operator to temporarily reduce feed-in and off-take whenever local grid conditions require it.
For the industry, that mainly means one thing: uncertainty. There is still little reliable benchmark data, whether on the specific design of these agreements or their technical implementation — yet the concrete design of an FCA has a direct impact on the economic viability of a storage project.
We wanted to get to the bottom of this question, so we ran a restriction analysis on the three FCA design variants defined by MITNETZ STROM.
You can find all results within the Short Analysis (only in German available):
Two Levers Controlled by the Grid Operator
Two factors influence the revenue structure of a battery storage system in the MITNETZ grid area:
the technical connection conditions (TAB) under Section 19 EnWG and Section 20 NAV — specifically, the permissible aFRR ramp rate, and
the chosen FCA variant.
MITNETZ STROM has defined three FCA design variants for its grid area. All three limit the power band for feed-in and off-take based on the PV and wind output of a reference plant. The difference lies in the threshold at which the limitation kicks in — the lower this threshold, the stricter the restriction.
The Methodology
For the analysis, we examined a hypothetical grey-power standalone storage system (10 MW / 20 MWh) in the MITNETZ region, using a backtest for the year 2025. The reference scenario is the storage system operating unrestricted, freely optimized across all markets using a multi-market strategy — without any TAB or FCA limitations.
We compared this reference scenario against two TAB scenarios (a slow and a fast aFRR ramp) combined with all three FCA variants, and determined the resulting effect on trading profit in each case.
The Results
The differences are substantial: depending on the combination of TAB scenario and FCA variant, the storage system's revenue drops by between 16.5% and 47.6% compared to the reference scenario.
Two factors determine the extent of this loss
The TAB ramp rate acts as a base effect: a slow aFRR ramp significantly worsens the FCA-related losses in every variant compared to a fast ramp.
The threshold of the FCA variant acts as an amplifier: moving from the mildest to the strictest variant nearly doubles to triples the absolute loss, regardless of the TAB scenario.
For the planning and economic assessment of standalone storage systems in the MITNETZ area, the specific design of the grid connection is therefore a key value driver — both the negotiated aFRR ramp rate and the chosen FCA variant should be factored into site evaluation early on.
The Full Analysis
The short analysis (only available in German) includes a detailed overview of all three FCA variants, the underlying TAB scenarios, and the complete revenue table covering all six scenario combinations examined.
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