GC0185: Grid Code Changes for Mandatory Frequency Response (MFR) replacement
What is being proposed
NESO are launching a new response service (Real-time Dynamic Regulation) in 2026/27 to replace Mandatory Frequency Response (MFR). It is expected that the two products will run in parallel to 2029 to enable transition, before phasing out procuring of MFR.
Current status
The proposal will be presented at the January Grid Code Review Panel. 09/03/2026: The Panel agreed by majority that GC0185 does not have a clearly defined defect and scope and requested the Proposer to return to the March Grid Code Review Panel with a clarified defect and scope.
Details
Timeline
Analysis
NESO proposes Grid Code changes to replace Mandatory Frequency Response (MFR) with a new Real-time Dynamic Regulation service from 2026/27. The two products will run in parallel until 2029 before MFR is phased out. The Panel rejected the initial proposal in March 2026 for lacking clarity on defect and scope.
Why it matters
This shifts frequency response from mandatory provision by generators to a procured service, converting a regulatory obligation into a market-based mechanism. However, the parallel operation until 2029 creates dual costs and complexity, while the Panel's rejection suggests the economic case remains unclear.
Key facts
- •Real-time Dynamic Regulation launches 2026/27
- •Parallel operation with MFR until 2029
- •Grid Code Review Panel rejected initial proposal March 2026
- •Cross-code impact includes CUSC changes