The European Union (EU) Network Code on Requirements for Generators (NC RfG) defines the technical requirements that generating and storage units must comply with prior to connecting to the power grid. While it entered into force in 2016, it is currently undergoing an amendment process to reflect the latest changes in the European power grid, including more robust requirements in the context of a growing penetration of converter-based generation and storage.

The amended Regulation, the so-called NC RfG 2.0, is expected to enter into force by the end of 2026/early 2027. The draft version consultated by the European Commission (EC) during July and August 2026 includes non-exhaustive grid forming requirements for non-synchronous generating and storage units, such as synthetic inertia provision and voltage source behind an impedance behaviour. These requirements vary depending on the type (i.e size) of unit, being mandatory for some cases while subject to a national decision for others.

Once the NC RfG 2.0 enters into force, the European Network of Transmission System Operators for Electricity (ENTSO-E) is legally mandated to draft Implementation Guidance Documents (IGDs), publicly consult them, and publish them within 6 months after the entry into force. These documents aim at guiding system operators, which are not bound to follow them, with the national implementation of the non-exhaustive EU NC RfG 2.0 requirements that must be exhaustively defined in the national Regulations.

This is the case for the grid forming requirements of NC RfG 2.0 and, consequently, ENTSO-E is currently developing an IGD on this topic. This IGD builds on the previous ENTSO-E's report from the Technical Group on Grid Forming Capability (TG GFC), where ENTSO-E engaged with relevant stakeholders and included their feedback. The report was publised in November 2025 and available here: https://www.entsoe.eu/news/2025/11/04/entso-e-publishes-phase-ii-technical-report-on-grid-forming-requirements/.

In a nutshell, the main outcomes of the ongoing IGD will be presented. The IGD proposes detailed requirements on the grid forming requirements of the draft NC RfG 2.0: i.e., on the voltage source behaviour behind an impedance within capability limits, on the synthetic inertia contribution within capability limits, and on the behaviour when reaching capability limits. Furthermore, it also recommends some principles to verify compliance with these requirements.