Grid-forming storage: Europe’s next requirement for inverters and PCS
Europe’s draft grid-connection code for generators (NC RfG 2.0) makes grid-forming capability mandatory for larger power park modules, including energy storage of 1 MW and above. Here is what it means for converter makers.
- 01ENTSO-E published its final technical report on grid-forming requirements for power park modules in November 2025.
- 02The draft NC RfG 2.0 makes grid-forming capability mandatory for type B, C and D modules.
- 03Storage of 1 MW and above — including large bidirectional V2G sites — falls within scope.
- 04Requirements apply to new connections and substantial modifications, after national implementation.
- 05Check the Official Journal for adoption status; national grid codes apply until then.
Why grid forming
As inverter-based generation and storage replace synchronous machines, power systems lose the inertia and voltage stiffness those machines provided. Grid-following inverters measure the grid and inject current to match it. Grid-forming inverters instead behave as a voltage source: they hold voltage and frequency, respond to disturbances immediately and share load like a synchronous generator.
What Europe is preparing
The EU network code on requirements for generators (NC RfG) sets technical rules for connecting generating units. A revised version, often called NC RfG 2.0, has been in preparation since ACER sent its recommendation to the European Commission in December 2023.
In November 2025, ENTSO-E published its final technical report on grid-forming capability of power park modules. Under the draft:
| Item | Draft position |
|---|---|
| Who | Power park modules of type B, C and D; type A optional |
| Storage | Energy storage modules of 1 MW and above, including bidirectional V2G sites |
| What | Voltage-source behaviour: voltage control, inertial response, frequency support, damping |
| When | New connections and substantial modifications, after national implementation |
After adoption, ENTSO-E plans an implementation guidance document with the detailed requirements, and national transmission system operators will set parameters and transition periods.
What it means for inverter and PCS makers
- Control architecture. Grid-forming is a control and hardware question: current headroom, DC-side energy and fast protection all influence what a converter can deliver.
- Model validation. Grid operators increasingly ask for validated simulation models, so test data and models have to match.
- New test cases. Expect tests for phase-angle jumps, frequency ramps (RoCoF), voltage dips with current limitation, islanding behaviour and oscillation damping, in addition to today's fault-ride-through tests.
- Market timing. Projects connecting in the second half of the decade may need grid-forming capability. Developing and validating it takes time.
Where things stand
As of this writing, check the EU Official Journal for the final adoption of NC RfG 2.0 and your target country's grid code for transition rules. Until national implementation, existing requirements such as EN 50549 and national codes (VDE-AR-N 4105/4110, CEI 0-21 and others) apply.
Our partner laboratory network tests PV inverters and energy storage converters up to 2.5 MW, including grid-forming and grid-following modes, fault ride-through and power-quality behaviour.
FAQ
Is grid forming already mandatory in the EU?
Not EU-wide yet. It is in the draft NC RfG 2.0; after adoption, national implementation sets dates and transition periods. Some grid operators already request it in tenders.
Does it apply to small residential inverters?
The draft makes it mandatory for type B to D modules and optional for type A, the smallest category.
Can a grid-following inverter be updated by firmware?
Sometimes partly, but grid forming often needs extra current headroom and DC-side energy. Assess the hardware before relying on a firmware update.
Sources
CertificationEU CE & TÜV Marks 
