GC0166 goes live: enabling smarter use of limited duration assets

Limited duration assets, such as storage, will be able to provide clearer information on the energy they can deliver over time, supporting smarter decision-making for both real-time balancing and forward system planning in the Balancing Mechanism (BM), with GC0166 now live in the Electricity National Control Centre (ENCC).

What is GC0166?

The changes introduce two new parameters – Maximum Delivery Offer (MDO) and Maximum Delivery Bid (MDB). These give clearer information on how much energy assets like storage can deliver over time. This helps us make better decisions to balance the system in real-time and plan ahead with more confidence in scheduling timescales.

Taking a controlled rollout, five units across four lead parties are now submitting MDO and MDB data. This allows us to confirm systems and processes are working as expected before we scale-up.

Benefits of GC0166

The benefits of these changes are clear:

• Better visibility of available energy
  • Giving us better understanding of the capabilities of limited duration assets 
• More accurate scheduling decisions
  • Supporting efficient system balancing and planning 
• Improved use of flexible technologies like storage
  • Critical to operating a low-carbon system
• Greater system efficiency and value for consumers
  • Supporting a reliable, clean and affordable electricity system

Delivered through industry collaboration

The changes have been shaped through close collaboration with industry. NESO, Elexon, market participants and software providers have worked together from design through to delivery and testing to ensure the changes delivers practical value.

Craig Dyke, Director of System Operations, said:

“This is a key milestone in being able to improve utilisation of the increasing volume of limited duration assets.”

He emphasised the importance of continuing to work closely with market participants during the transition, noting that collaboration and learning will be critical to ensuring new data submissions align with expectations and deliver value.

Craig also highlighted that the benefits of GC0166 will be realised progressively, as more units adopt the new parameters and industry familiarity with the data increases.

What’s next? 

Implementation will continue in phases; the benefits of GC0166 will be realised progressively as more units adopt the new parameters.

Continuing to work closely with Industry during the transition will be important to achieving the greatest impact out of the changes. 

Operational implementation of the new dynamic parameters is required by 5 November 2026, to ensure compliance with the Grid Code.

Further information and support

Guidance and technical documents are available to support participants through the transition: 

• Data Validation, Consistency and Defaulting Rules – rules on the submission of MDO and MDB
• Electronic Dispatch & Logging (EDL) Message Specification – message structure used on EDL for MDO and MDB
• Wider Access API Message Specification – message structure used for MDO and MDB accessible on the Wider Access API Developer’s Portal
• MDO/MDB Best Practice Guidance (Version 2) – Supplementary information incorporating enhancements proposed by industry participants 

Get in touch

If you’re organisation is operating as the Lead Party for limited duration assets, which are live in the Balancing Mechanism, and you haven’t received any communication from NESO, please contact the team at [email protected]