Enduring Auction Capability (EAC)

EAC results file for data portal

As we proceed with development of the Enduring Auction Platform (EAC), we can now provide templates of the results files that market providers will be able to access post-auction via the data portal.

EAC results - sell orders

EAC results format

EAC results summary 

EAC results by unit

EAC results - buy orders

Sell Order Design – 19 January 2023 

As part of the SMP Show and Listen workshop on 19 January 2023, we presented the format of the sell order design for the EAC as part of our work for the Detailed Design phase of the project.  

Download the EAC Sell Order Design

Watch the EAC Sell Order Design presentation

We recently held a number of consultation drop-in sessions, providing market participants with support following the release of Article 18 EBR consultation for the Enduring Auction Capability (EAC).

Below you can find the session recordings alongside an example spreadsheet for calculation of settlement values that participants can use to visualise the changes to the settlement calculation, and see how much they would be paid (or pay ESO) for different clearing prices and performance factors.

EAC Roadmap - July 2023

Consultation drop-in session - 05/07/23

Consultation drop-in session - 07/07/23

Consultation drop-in session - 12/07/23

Example spreadsheet for calculation of settlement value

CIAM URL changes:

The EAC production environment will be unavailable from 7:00 AM to 8:00 AM on 27th November 2025 as we implement CIAM URL updates.

From 8:00 AM, the following CIAM endpoints will switch to:

• OpenID Configuration
  https://signin.neso.energy/as/.well-known/openid-configuration
• Authorisation Endpoint
  https://signin.neso.energy/as/authorize
• Token Endpoint
  https://signin.neso.energy/as/token
• Token Introspection
  https://signin.neso.energy/as/introspect
• Token Revocation
  https://signin.neso.energy/as/revoke
• User Info Endpoint
  https://signin.neso.energy/as/userinfo
• Signoff Endpoint
  https://signin.neso.energy/as/signoff

The EAC Production UI and EAC GraphQL API Endpoint will remain unchanged:

• https://eac.neso.production.n-side.com/marketparticipant
• https://eac.neso.production.n-side.com/market-participant/api/graphql

This is a permanent change for the EAC production environment. 

Note: The CIAM URL has already been updated for the EAC sandbox environment since 9 October 2025. Please refer to previous release notes for more information. 

Industry drop-in session – 9th December

We will be holding a drop-in session on Tuesday 9th December at 10:30am which will demo some UI changes we have made to the EAC platform in preparation for Slow Reserve in March 2026.

To register your attendance to this session, sign up here

The auction timing for Balancing Reserve will move from 08:15 to 14:00 local time (UK) to co-optimise with the day-ahead auctions for Dynamic Response services and Quick Reserve.

• The final Balancing Reserve morning auction, "Balancing Reserve @ 08:15", will take place on Tuesday, 28 October at 08:15. After this date, all BR submissions will need to be entered into the afternoon auction.
• The current co-optimised Dynamic Response and Quick Reserve auction, "Response & QR @ 14:00", will be renamed to "Response & Reserve @ 14:00" and will include the Balancing Reserve service. The renamed auction will appear as an upcoming auction from Wednesday, 15 October, with the first auction taking place on Wednesday, 29 October. After this date, providers will only see this auction on the EAC platform.
• Auction results will be published here from Wednesday, 29 October.
• For more information, please visit here.

Note: The EAC sandbox environment will mirror production. In sandbox, the Balancing Reserve morning auction will expire on 28 October, and from 29 October onwards, there will be only one auction per day.

The EAC sandbox environment will be unavailable from 10:00 AM to 2:00 PM on 9 October 2025 to implement CIAM URL updates.

From 2:00 PM, the following CIAM endpoints will switch to:

• OpenID Configuration
  https://preprod.signin.neso.energy/as/.well-known/openid-configuration
• Authorisation Endpoint
  https://preprod.signin.neso.energy/as/authorize
• Token Endpoint
  https://preprod.signin.neso.energy/as/token
• Token Introspection
  https://preprod.signin.neso.energy/as/introspect
• Token Revocation
  https://preprod.signin.neso.energy/as/revoke
• User Info Endpoint
  https://preprod.signin.neso.energy/as/userinfo
• Signoff Endpoint
  https://preprod.signin.neso.energy/as/signoff

The EAC Sandbox UI and EAC GraphQL API Endpoint will remain unchanged:

• https://sandbox.eac.neso.production.n-side.com/marketparticipant
• https://sandbox.eac.neso.production.n-side.com/market-participant/api/graphql

This is a permanent change for the EAC sandbox environment. The production environment URLs remain unchanged.

Auction results for the 2PM Response and Reserve auctions will be archived on 23 September 2025, after publishing the daily auction results. 

Results for delivery dates on and after 1 April 2025 will remain in the current dataset. The resource IDs will remain unchanged, and the file names will be:

• NESO Response-Reserve Results Summary
• NESO Response-Reserve Buy Orders
• NESO Response-Reserve Sell Orders
• NESO Response-Reserve Results By Unit

Results for delivery dates before 1 April 2025 will be archived. The archive file names will be:

• NESO Response-Reserve Results Summary FY2023-FY2024 (Archive)
• NESO Response-Reserve Buy Orders FY2023- FY2024 (Archive)
• NESO Response-Reserve Sell Orders FY2023- FY2024 (Archive)
• NESO Response-Reserve Results By Unit FY2023- FY2024 (Archive)

Both live and archived datasets will be published here.

Note: Auction results for the 8:15AM Balancing Reserve auction will remain unchanged, as the 8:15AM Balancing Reserve auction will move to the 2PM Response and Reserve auction soon.

The mock auctions will facilitate the transition of the Balancing Reserve from the 8:15 AM auction to the 2PM Response and Reserve auction.

• Mock Auction Environment: The Mock Auction environment will be available to access from Wednesday 10th September. All data in Sandbox will be transferred to Mock Auction environment on Tuesday 9th September.
  • Auction URL: https://mock-auction.eac.neso.production.n-side.com/marketparticipant
  • API credentials: Credentials used in the sandbox environment can also be used in the mock auction environment.
• Auction Dates: Mock Response and Reserve auctions, including 5 services (DC, DM, DR, BR, and QR), will be scheduled daily at 2PM from Monday 15th September to Sunday 21st September.
• Auction Results: Mock auction results will be published here. Results for auctions from 15th September to 19th September will be published on the same day. Results for auctions from 20th September to 21st September will be published on Monday 22nd September.
• How to Participate: All participants in the sandbox will automatically have access to Mock Auction environment, and do not require additional registration. If you are already in the sandbox and wish to add any additional units or if you are not in the sandbox environment, please contact [email protected] by the close of play on Tuesday 9th September.

The EAC sandbox update scheduled for 19 August 2025 includes the following improvements:

• Cloning Feature Fix: An issue with the cloning functionality in the Market Participant UI has been resolved.
• Report API Enhancements: Two new fields, "consecutive" and "groupID", have been added to the report API. These fields are specifically applicable to Slow Reserve and do not apply to Response, Balancing Reserve, or Quick Reserve services.

Starting from 11 August, Balancing Reserve will be added to the Response & Reserve @ 14:00 auction in the EAC sandbox environment. This update aims to facilitate the testing of a co-optimised auction of 5 services: DC, DM, DR, BR and QR.

The upcoming EAC Release on 25 June focuses on implementing a new validation rule to prevent overbidding and adding a new Linked Service Windows feature to prevent the crossover problems at service windows boundaries.

The release includes:

Prevent Overbidding

• A new validation rule to prevent overbidding is applied to baskets associated with battery units providing Response services. Detailed information on this rule is available in the release documentation.
• The sandbox environment will be updated with the overbidding feature from 20th June, we encourage providers to go in and test this ahead of the release in production on 25 June.

Linked Service Window (LSW)

• Introduction of the concept of Linked Service Windows to prevent the crossover problems at service windows boundaries. Initially, this feature will remain deactivated. NESO plans to provide advance notice to the market regarding the activation timeline. Market participants are encouraged to stay updated by following NESO communications for information on when this feature will become active.

API Changes

• Basket Composites feature added allowing providers to submit groups of baskets.
• The API documentation has been expanded with new sections on Basket Composites and the Linked Service Windows feature. The Postman Collection has also been updated with examples of the new queries and mutations.
• The API documentation (Home) will be updated after the release.

The upcoming EAC Release on 4th Feb includes significant improvements and fixes across multiple areas of the platform. This release focuses on enhancing API documentation.

The improvements include:

• API documentation: improve the section explaining how to retrieve the service windows, following a comment raised by a market participant and enhance section describing auction timings

The upcoming EAC Release on 4th Dec includes significant improvements and fixes across multiple areas of the platform. This release focuses on enhancing unit versioning capabilities, expanding order management functionalities, and improving overall platform accessibility.

The improvements include:

• Functionality to submit substitutable buy order families across:
  • Services with different service windows
  • Reserve and Response services
• Fixed cloning functionality in Market Participant UI
• Addressed maximum basket size limitation via API
• Improved bookmark handling for CIAM-registered users
• Added additional logging for invalid token usage
• Fixed various UI display inconsistencies
• Addressed order creation issues in the Operator UI

Data Portal files

Following our change from ESO to NESO, the EAC results files displayed on data portal will have their name changed.

From Monday 25 November the files displayed will be named:

• NESO Response-Reserve Results Summary 2023-2024
• NESO Response-Reserve Buy Orders 2023-2024
• NESO Response-Reserve Sell Orders 2023-2024
• NESO Response-Reserve Results By Unit 2023-2024

EAC Auction Results

AND

• NESO Balancing-Reserve Results Summary 2023-2024
• NESO Balancing-Reserve Buy Orders 2023-2024
• NESO Balancing-Reserve Sell Orders 2023-2024
• NESO Balancing-Reserve Results By Unit 2023-2024

EAC Auction Results