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v2.0Current version

Published04/02/2026Effective date06/02/2026Release date04/02/2026

Primacy Rules

Document Summary

What? This rule establishes DNO priority over the dispatch of the MW Dispatch Sub-Market.How? The rule set out the concept of DNO priority, the use-cases they relate to and the associated processes needed to implement it.Who? This impacts the DNOs with MW Dispatch deployed (currently NGED and UKPN), and NESO. As MW Dispatch is locational it only impacts generators within specific grid supply points (as set out by NESO and the DNOs)When? The rule will go live in January 2026 as systems and processes are already in place. Why? The rule aims to reduce conflicts and increase efficiency across the different Sub-Markets

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Primacy Rules - Flexibility Market Rules - Elexon

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0.0

Sections 1, 2, 3 and 4 form the legally binding Flexibility Market Rule.

Defined terms capitalised in this document shall have the meaning given in Section 4.

GuidanceSummary of Primacy Rules

This section is provided as guidance to the Flexibility Market Rule. Therefore, it is not legally binding and falls outside of the formal change management process.

Context

Primacy rules are used to manage situations of conflict between the actions of different System Operators. For example, NESO might ask a site to increase their generation, whilst the DNO is asking a nearby site to reduce. The Primacy rules set a framework for managing that conflict.

Since this rule codifies the first version of the Primacy Rules, it only applies to NESO, NGED and UKPN, specifically in areas where MW Dispatch is being procured.

Primacy Rules Requirements

The rule sets out some core requirements:

The System Operators must share information on potential conflicts via Risk of Conflict reports. DNOs need to be able to create these, and NESO must be able to ingest them
As DNO primacy is being implemented the DNO action has priority, and so NESO shall not take actions in the MWD sub-market that exacerbate the conflict (as identified in the Risk of Conflict report).

We believe the impact of these requirements to be:

Impact on System Operators	Impact on FSPs
NESO, NGED and UKPN must develop and maintain the processes and systems to delivery primacy	Providers of MW Dispatch may see lower dispatch identified in the Risk of Conflict report.

Implementation monitoring requirements

The key requirements are laid out below. A view across the rules is available in our deadline tracker.

Category

Requirement

Trigger for data submission

What we will do with it

Implementation tracking

Basic tracking of implementation status and target date

From 14/01/2026 (20 working days after the published date).

Within 10 days of change

Track whether implementation is on track via our Implementation tracker.

Flexibility Market Catalogue data

From 06/02/2026.

Within 10 days of change

Provide an overview of the sub-market and the market as a whole via the Flexibility Market Catalogue.

Effectiveness monitoring data

N/A

1Applicability of this Flexibility Market Rule

1.0

This Flexibility Market Rules applies only to NESO and DNOs supporting the operation of the MW Dispatch Sub-Market. Innovation trials are not bound by this Flexibility Market Rule.

The relevant System Operators shall develop and maintain the processes defined in section 2.3 to implement DNO Primacy as defined in section 2.2 in the use cases set out in section 2.4 no later than the Implementation Date.

The relevant System Operators shall provide the data set out in section 3 no later than the timings also set out in section 3.

Variations to this rule are only permitted with an approved Derogation from the Market Facilitator.

The core applicability parameters are laid out below.

Table 1: Flexibility Market Rule dates

Published Date	04/02/2026
Implementation Date	06/02/2026
End Date	-

2Primacy Rules

2.1What are Primacy Rules?

Primacy Rules are a defined set of principles and guidelines to manage conflicts between NESO and DNO requirements and constraints. They govern the procurement, planning, scheduling, and dispatch of supporting services across the electricity system. These rules are designed to enable efficient and transparent optimisation of both transmission and distribution networks, operated respectively by NESO and DNOs.

Primacy rules aim to resolve potential overlaps or conflicts between services by prioritising actions based on whole-system value, while distinguishing between market- or price-driven actions and essential operational requirements. They seek to balance the technical needs of local networks, system-wide operability risks, value for service providers, support for emerging market platforms, and cost impacts on consumers. I.e. primacy seeks to avoid a scenario where the dispatch of one System Operator’s service is contrary to the network or system requirements of another System Operator such that it results in increased protective actions (and therefore costs) or risks secure operation.

Primacy typically applies to conflicts between different assets within the same electrical network and may otherwise create inefficiencies.

2.2Definition of DNO primacy

DNO primacy means DNO flexibility services shall take priority over the NESO’s service, due to their localised nature and the limited availability of alternative options at the distribution level.

The Risk of Conflict report will be fed into the NESO’s planning processes for the relevant service, with the NESO removing units from the control room dispatchable options where the DNO has identified a risk of conflict unless such actions cause significant operational harm to NESO.

2.3Required processes to support primacy

The following supporting processes and data exchanges are needed to implement the primacy rules:

Asset mapping: Mapping relevant assets between the System Operators. This should cover the assets impacted by both services in the use case (as set out below). This is currently managed by the DNO, through the mapping of MW Dispatch requirements in its bilateral connection agreements with the NESO. The location of DNO CMZs is publicly available.
Forecasting the risk of conflict: The DNOs shall create a forecast of the risk of conflict. This will reflect the DNO’s specific approach to forecasting and translate it into the identification of risk of conflict.
Sharing the risk of conflict report: DNOs shall share a regular Risk of Conflict report with NESO. This should be updated no less frequently than weekly and include at a minimum:
- A common ID
- The start and end time of the unavailability
- An unavailability reason (this specifies if the asset will be constrained or not by the DNO)
- An unavailability cause (to allow for further use cases to be added).
NESO integration process: NESO will ingest the forecast and feed into their procurement & dispatch processes.

2.4Applicable use cases

The current use-cases under consideration are highlighted in Table 2 below.

Table 2: Applicable use cases for the Primacy Rules

Relevant NESO Sub-Market	Relevant DNO Sub-Market	Applicable Rule
MW Dispatch	All DNO Sub-Markets except Restore & Operational Utilisation	DNO has Primacy

3Market Information

3.1Implementation tracking

The relevant System Operators must provide the Market Facilitator with the data set out in Table 3 for each Sub-Market in scope of this Flexibility Market Rule. The data provided should accurately reflect their implementation of the rule within each of each Sub-Market.

The expected values required for compliance are also set out in Table 3.

Initial data shall be sent no later than 20 working days after the Published Date of this Flexibility Market Rule.

Updates shall be sent as soon as reasonably practical, and no later than 10 working days after any changes to the values.

Elexon reserves the right to publish this data within its Implementation Tracker.

Table 3: Implementation tracking requirements

FMR-MRS	Parameter	Required value (per Sub-Market)
Implementation Status	Dependent on date: Before Implementation Date: Not yet started, Implementing, Paused, Implemented Between Implementation Date and End Date: Implemented After End Date: Superseded
Target Implementation Date	No later than Implementation Date

FMR-MRS

Parameter

Required value (per Sub-Market)

Implementation Status

Dependent on date:

Before Implementation Date: Not yet started, Implementing, Paused, Implemented
Between Implementation Date and End Date: Implemented
After End Date: Superseded

Target Implementation Date

No later than Implementation Date

3.2Flexibility Market Catalogue data

The relevant System Operators must update the Market Facilitator with the data set out in Table 4 below for each Sub-Market in scope of this Flexibility Market Rule. This should accurately reflect their implementation of each Sub-Market.

The expected values required for compliance are also set out in Table 4.

Initial data shall be sent no later than the Implementation Date of this Flexibility Market Rule.

Updates shall be sent as soon as reasonably practical, and no later than 10 working days after any changes to the values.

The relevant System Operators shall also publish this information themselves.

Elexon reserves the right to publish this data within its Flexibility Market Catalogue.

Table 4: Sub-Market definitions

	Parameter Name	Description	Required value
NESO: for all DNO Sub-markets in scope of this rule as set out in section 2.4	Is DNO primacy implemented	Has DNO priority, as defined in section 2 been implemented?	Yes for applicable Sub-Market pair as set out in section 2.4.
DNOs: for all NESO Sub-markets in scope of this rule as set out in section 2.4	Is DNO primacy implemented	Has DNO priority, as defined in section 2 been implemented?	Yes for applicable Sub-Market pair as set out in section 2.4.

3.3Effectiveness monitoring

There are no market facilitator metrics for this rule

4Glossary

4.0

The following definitions are specific to this Flexibility Market Rule. These are supplemented by the definitions in the Market Facilitator Glossary. If there is an inconsistency between definitions, the definition in this document shall prevail.

FMR: Primacy Rules - Amendment record

Guidance

This section is provided as guidance to the Flexibility Market Rule. Therefore, it is not legally binding and falls outside of the formal change management process.

Version	Published Date	Document Status	Description of Changes	Change Proposal Reference	Market Facilitator Decision Report Ref
1.0	12/12/2025	Final	Document Published	-	-
2.0	04/02/2026	Final	Housekeeping change	CP002	CP002

4.0.2

Annex 1: Associated meta-data

Guidance

This annex is provided as guidance to the Flexibility Market Rule. Therefore, it is not legally binding and falls outside of the formal change management process.

Identifier	FMR-PR
Title	Primacy Rules
Type	Flexibility Market Rule
Collection	Market Coordination
Audience	NESO, DNOs, Flexibility Service Providers
Expertise	Operations
Owner	Market Facilitator
Expected benefit	To manage conflict between system operators to reduce overall system costs and reduce risk to security of supply
Related end-to-end process reference	C.3 Clear Market D.3 Dispatch Units
References
IsReferencedBy
Published version number	2.0
Applicability	Only NESO and DNOs supporting the operation of the MW Dispatch Sub-Market.
Published Date	04/02/2026
Implementation Date	06/02/2026
End Date	N/A
Terms of variations	Approved Derogation only
IsReplacedBy	N/A
Replaces	N/A
Status	Final
Change since last version	Housekeeping change – Correction of Implementation date. Update to table numbering, section 3.3 and sub-market guidance.
Description	What? This rule establishes DNO priority over the dispatch of the MW Dispatch Sub-Market. How? The rule set out the concept of DNO priority, the use-cases they relate to and the associated processes needed to implement it. Who? This impacts the DNOs with MW Dispatch deployed (currently NGED and UKPN), and NESO. As MW Dispatch is locational it only impacts generators within specific grid supply points (as set out by NESO and the DNOs) When? The rule will go live in January 2026 as systems and processes are already in place. Why? The rule aims to reduce conflicts and increase efficiency across the different Sub-Markets