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Published18/03/2026Effective date01/04/2026Release date18/03/2026

Standard Baselining Methodologies

Document Summary

What? This rule sets out the minimum expectation for the use of standardised baselining methodologies in DNO markets. How? The rule defines different types of baselining techniques that should be used in defined criteria/circumstances. It defines the minimum accuracy requirements for Nomination baselines, expectations on following the principles of good industry practice for developing Nomination baselines, escalation routes and enhanced monitoring. It also sets out the requirements for the use of any alternatives to the defined methodologies. It sets out requirements for stakeholders to share/submit information to meet this rule. Who? This rule impacts all DNOs, FSPs and market platform providers. When? This rule comes into force on 01/04/2026 Why? The rule aims to provide a standard approach to the use of baselining methodologies in DNO markets.

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Standard Baselining Methodologies - Flexibility Market Rules - Elexon

Means, over an assessment period, the calculated average absolute error of a Meterable Unit.

a non-DBM baselining approach where the applicable DBM is not suitable due to the DER having atypical characteristics or operational behaviours.

a baselining technique which assumes the participating DER operates at its full rated capacity during the flexibility event, irrespective of actual operational conditions.

the baselining methodology that will be utilised in the assessment of the performance of the DER. This will either be the relevant DBM, or, where approved by the DNO, the ABM.

energy resources comprised of generation and/or storage and/or controllable load, which is connected at the low or medium voltage distribution level.

the baselining methodology that should be applied based on the Location Type, Metering Location, Technology Type and direction of the service (i.e. DTD/GTU or DTU/GTD).

a day that can be excluded from a Recent History baseline methodology for activities such as delivery of Balancing Services, Virtual Trading, Site Outage, Equipment and/or Site Disconnection occurring on that day.

a baselining technique which uses a fixed daily profile derived from the observed energy behaviour of a representative group of DERs that represents normal operating behaviour or a DNO’s planning scenarios.

either a domestic premise or an Industrial & Commercial (I&C) premise.

an aggregated collection of DERs, or a single DER, that are either all a non-Nomination DBM or all a Nomination DBM.

a location for the metering either at the Point of Connection to the Distribution System (i.e. the Boundary Point Metering System) or a behind the Boundary Point Metering System located at the asset providing the flexibility service.

Means, over an assessment period, the calculated average net error of a Meterable Unit. A negative net error indicates Nominations are higher than the Meterable Unit’s normal behaviour, while a positive error indicates the Nominations are under the Meterable Unit’s normal behaviour.

a baselining technique which uses an estimated/expected set of meter values, provided by the Flexibility Services Provider (FSP), based on the expected or normal operation of the site / DER without any flexibility event, for a future availability window that then becomes a utilisation event.

a baselining technique which uses a set of recent, eligible days (i.e. excluding Event Days such as a day providing a flexibility service) preceding a utilisation event. This may also include correction factors such as within-day adjustments for weather variables or removal of outlier values.

the type of Distributed Energy Resource (DER) which is the asset providing the flexibility service. For example, an EV Charger.

a baselining technique where the baseline energy consumption or generation is set to zero, meaning no energy usage or production is assumed in the absence of the utilisation event.

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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 Standard Baselining Methodologies Flexibility Market Rule

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

The purpose of this rule is to introduce standardised baselining methodologies and processes to Distribution Network Operator (DNO) markets. Baselines set the level from which performance is calculated, and so are a key element of the commercial proposition for flexibility services.

Baselining Requirements

This Flexibility Market Rule specifies the allowed baselining techniques for DNO markets. These include:

Asset Capacity (set by the capacity of the asset),
Fixed Reference (based on standardised view of such an asset),
Zero, and
Nomination (set by the FSP).

The rule sets one of these as the Default Baselining Methodology (DBM) based on:

Whether the site is domestic or an Industrial & Commercial site;
Whether the metered point is Point of Connection or at the Asset;
The technology type; and
Direction of the service being offered (i.e. Demand Turn Down/Generation Turn Up or Demand Turn Up/Generation Turn Down).

Individual Assets can be combined into Meterable Units and an aggregated baseline is provided. Default Baseline Methodologies that are non-Nomination type cannot be combined with Nomination type baselines.

An Alternative Baselining Methodology (ABM) process is available where sites and Assets have atypical characteristics or operational behaviours, or a provider wants to combine a non-Nomination and a Nomination Default Baselining Methodology into a Meterable Unit. The DNO must approve this request.

We believe the impact of these requirements to be:

Impact on System Operators

Impact on FSPs

DNOs must use this methodology to determine baselines. This includes setting out Fixed Reference Baseline values as required for each DBM.

They also need to develop a process for the ABM requirements. This includes accepting, processing and analysing applications; publishing key deadlines; notification to applicant of decision to approve or reject; report to Market Facilitator number of approved ABMs approved.

Finally, to support Nomination Baselines, they need to develop a process for the Nomination Baseline justification requirements. This includes accepting, processing and analysing Nomination justifications; notification to applicant of decision to approve or reject; instigating a Nomination Performance Review and reporting volumes to Market Facilitator. They also need to develop a process to assess the accuracy of the Nomination Baseline for both Net % and Absolute % Error as per the requirements of this rule; report results to the Market Facilitator.

The new baselining methodology will be used to assess the performance of FSPs. As such they must understand what baselining will be used for their assets.

They must also adhere to the limitations surrounding to the components of meterable units for certain baselining combinations.

Finally, where Nomination Baselines are used they must develop a process to determine a Nomination baseline in line with the principles of good industry practice as laid out in this rule; and participate in Nomination Performance Reviews as required.

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

Confirmation of use of standardised methodologies and associated processes

From 01/04/2026.

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

Monitoring of ABM requests; Nomination baseline accuracy; number of performance reviews

Every 3 months

Track the effectiveness of the DBM against number of ABM requests; and of nomination methodology process and performance of parties.

Tracked via our Effectiveness Monitoring Report

Derogations against this rule

The following derogations are in place:

Who	What	For how long	Why
SSEN	The full requirements	Until 01/07/2026	To allow for robust implementation
SSEN	The full requirements for LMA Interim Payment Service	Until 01/02/2027	To prevent blockers to LMA Interim Service settlement
NGED	Sections 2.2, 2.3, 2.4 and 2.6	Until 31/03/2027	To allow for robust implementation and initiation of Change Process

1Applicability of this Flexibility Market Rule

1.0

This Flexibility Market Rule applies to all Distribution Network Operator (DNO) Sub-markets within the Market Facilitator scope.

Innovation trials are not bound by this Flexibility Market Rule.

All DNOs shall adopt the baselining methodology set out in section 2, for any contracts awarded after the Implementation Date.

All DNOs 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 dates for this Flexibility Market Rule are laid out below.

Table 1: Flexibility Market Rule dates

Published Date	04/02/2026
Implementation Date	01/04/2026
End Date	-

2Baselining Methodology

2.1Standard Baselining Methodologies definitions

The baselining methodologies used in this Flexibility Market Rule are outlined in Table 2 below.

Table 2: Baselining methodologies

Name	Definition
Asset Capacity	Assumes the participating Distributed Energy Resource (DER) operates at its full rated capacity during the flexibility event, irrespective of actual operational conditions.
Fixed Reference	Uses a fixed daily profile derived from the observed energy behaviour of a representative group of DERs that represents normal operating behaviour or a DNO’s planning scenarios.
Nomination	Uses an estimated/expected set of meter values, provided by the FSP, based on the expected or normal operation of the site / DER without any flexibility event, for a future availability window that then becomes a utilisation event.
Recent History	Uses a set of recent, eligible days (i.e. excluding Event Days such as a day providing a flexibility service) preceding a utilisation event. This may also include correction factors such as within-day adjustments for weather variables or removal of outlier values.
Zero	The baseline energy consumption or generation is set to zero, meaning no energy usage or production is assumed in the absence of the utilisation event.

GuidanceExplainer: What does a baselining methodology look like in practice?

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.

A simplified example for each baselining methodology specified in Table 1 is provided in this section. These examples are non-exhaustive and do not cover all circumstances where they would be used (e.g. only one direction of service is shown).

Asset Capacity

This methodology assumes the participating DER operates at its full rated capacity (no de-rating) during the flexibility event, irrespective of actual operational conditions. Worked examples of these principles are shown below for a Schedulable Generation DER which has a full rated export capacity of 5MW. In the example, the Generation DER has a Generation Turn Down contract for 2MW.

The DER turns down generation from 5MW to 3MW and is paid for 2MW as the baseline was set at 5MW (i.e. the full rated capacity) and the measured power during the Service Window was 3MW.

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.

Baseline (MW)

Measured Power (MW)

Data table

Category	Baseline (MW)	Measured Power (MW)
15:00	5	4.7
15:30	5	4.9
16:00	5	4.8
16:30	5	4.9
17:00	5	3
17:30	5	3
18:00	5	3
18:30	5	3.1
19:00	5	3.1
19:30	5	4.1
20:00	5	4
20:30	5	4.8

Fixed Reference

This methodology uses a fixed daily profile derived from the energy behaviour of a representative group of DERs that represents normal operating behaviour or from a DNO’s planning scenarios.

In the example shown below, the baseline value represents a reference, non-smart charging behaviour for a large group of domestic EV charging points.

It is this representative behaviour that is used to set the baseline value of -5MW to assess the level of Demand Turn Down provided by the DER. The measured output during the Service Window is -3MW, therefore it is deemed to have delivered a dispatched capacity of 2MW.

Baseline (MW)

Measured Power (MW)

Data table

Category	Baseline (MW)	Measured Power (MW)
15:00	-4.2	-4.8
15:30	-4.6	-5
16:00	-4.9	-4.9
16:30	-4.8	-5
17:00	-4.9	-3
17:30	-5	-3
18:00	-5	-3
18:30	-5	-3.1
19:00	-4.9	-3.2
19:30	-4.8	-4.1
20:00	-4.4	-4
20:30	-4.6	-4.8

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.

The above example covers the scenario where there is a reduction or increase in consumption and generation. Where the delivery of flexibility by a DER (e.g. Intermittent Generation, Storage and EV Charger V2G) results in a swing from prevailing Active Energy Import to Active Energy Export (or vice versa) which will typically be where the FSP uses a Point of Connection metering arrangement at a domestic site (not relevant to Industrial and Commercial (I&C) sites as Point of Connection uses Nomination) there may be a need to assess flexibility delivery in comparison to the Fixed Reference Baselines across both the Import and Export MPANs for the site.

Zero

The baseline energy consumption or generation for this methodology is set to zero, meaning no energy usage or production is assumed in the absence of the utilisation event.

In the example shown below, the DER is deemed to have provided a dispatched capacity of 2MW through a Generation Turn Up service as the measured output during the Service Window was 2MW.

Baseline (MW)

Measured Power (MW)

Data table

Category	Measured Power (MW)	Baseline (MW)
15:00	0.05	0
15:30	0.05	0
16:00	0.05	0
16:30	0.1	0
17:00	1.9	0
17:30	2	0
18:00	2	0
18:30	2	0
19:00	0.3	0
19:30	0.05	0
20:00	0.05	0
20:30	0.05	0

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.

Nomination

This methodology uses a proposed estimated/expected set of meter values / data, provided by the FSP, based on the expected or normal operation of the site / DER without any flexibility event, for a future availability window that then becomes a utilisation event. The timelines for submission of a Nomination baseline are detailed in the Nomination Baselining Methodology Submission Deadline section of this Flexibility Market Rule.

Nomination values may differ over the Service Window or be a single value that is applied for the whole Service Window.

As nomination baseline methodologies rely on FSPs to propose the values used, there will be accuracy standards that the DNO requires the FSP’s nominations to adhere to, to ensure the nominated values accurately reflect normal operating behaviour. This is detailed in the Nomination Baselining Methodology Accuracy section of this Flexibility Market Rule.

In the example shown below, a variable nomination value has been proposed by the FSP (-5MW for the earlier part of the Service Window and -4MW for the later part). In this scenario, the DER is paid for a dispatched capacity of 2MW of Demand Turn Down for the first part of the Service Window and a dispatched capacity of 1MW for the latter part.

Baseline (MW)

Measured Power (MW)

Data table

Category	Baseline (MW)	Measured Power (MW)
15:00	-5	-4.7
15:30	-5	-5
16:00	-5	-4.8
16:30	-5	-5
17:00	-5	-3.2
17:30	-5	-3
18:00	-4	-3
18:30	-4	-3
19:00	-4	-3.2
19:30	-4.1	-4.1
20:00	-4.1	-4
20:30	-4.1	-4.8

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.

Recent History

This methodology uses a set of recent, eligible days preceding a utilisation event and will complete an assessment based on the same time of day (i.e. 30-minute window) and type of day (i.e. working day or non-working day). This may also include correction factors such as a within-day adjustment for something like weather variables or removal of outlier values (typically defined as Event Days).

Event Days can include activities such as delivery of Balancing Services, Virtual Trading, Site Outage, Equipment and/or Site Disconnection.

In the example shown below, a DER baseline of 4.5MW for a Service Window on a Friday is set based on the mean average of the 10 most recent working days, which weren’t Event Days. Weekends and the Purple coloured Thursday (which met the criteria to be defined as an Event Day) are therefore excluded from the calculation. The measured power during the Service Window was 2.5MW of generation, and therefore, the DER is paid for a dispatched capacity of 2MW of Generation Turn Down.

Excluded (Event Day)

Excluded (Weekend)

Measured Power (MW)

Data table

Category	Measured Power (MW)	Excluded (Event Day)	Excluded (Weekend)
Thursday	4.9	0	0
Friday	4.1	0	0
Saturday	0	0	3.2
Sunday	0	0	3.4
Monday	4	0	0
Tuesday	4.7	0	0
Wednesday	5	0	0
Thursday	0	3	0
Friday	4.5	0	0
Saturday	0	0	3.8
Sunday	0	0	3.7
Monday	4.4	0	0
Tuesday	4.6	0	0
Wednesday	4.2	0	0
Thursday	4.2	0	0
Friday	2.4	0	0

Examples of other schemes, which are not in scope of this Flexibility Market Rule that use a recent history baseline are:

Balancing Settlement Code (BSC) historical baseline used for the Balancing Mechanism by Virtual Lead Parties (VLPs) and for Virtual Trading Parties (VTPs) in the wholesale market based on the Baselining Methodology Document. This includes a within-day adjustment for use in the Balancing Mechanism.
NESO Demand Flexibility Service (DFS), where the ‘DFS Participation Guidance document’ details an example of the Operational Baseline calculation in Appendix 5.
Capacity Market Rules use a historical baseline, as defined in Schedule 2 (‘Baseline Methodology’), for Demand Side Response (DSR) Capacity Market Units (CMUs).

2.2Default Baseline Methodologies

The Default Baseline Methodologies (DBM) set out the expected baselining methodology in a given scenario.

The DBM have been designed to align with the variables included in the Standard Pre-Qualification Criteria of:

Asset Scale (i.e. Domestic or I&C).
Metering Arrangement (i.e. Point of Connection Boundary Point Metering System or Asset Metering System at, or part of the Asset providing the flexibility service).
Technology Type (i.e. the type of DER which is the asset providing the flexibility service).
Demand Turn Down (DTD) / Generation Turn Up (GTU) or Demand Turn Up (DTU) / Generation Turn Down (GTD).

The DBMs are shown in Tables 2 (Domestic) and 3 (I&C) below:

Table 2: DBMs for Domestic DER

Asset Scale	Metering Arrangement	Technology Type	DTD / GTU	DTU / GTD
Domestic	Asset Level	Schedulable Generation	Zero	Asset Capacity (no de-rating)
		Intermittent Generation	Zero	Asset Capacity (no de-rating)
		Storage	Zero
		Heat Pump	(Asset Level) Fixed Reference
		EV Charger DSR
		EV Charger V2G
		Flexible Site Demand
	Point of Connection	Schedulable Generation	Zero + (Flexible Site Demand) Fixed Reference	Asset Capacity (no de-rating) + (Flexible Site Demand) Fixed Reference
		Intermittent Generation	Zero + (Flexible Site Demand) Fixed Reference
		Storage	Zero + (Flexible Site Demand) Fixed Reference
		Heat Pump	(Asset Level) Fixed Reference + (Flexible Site Demand) Fixed Reference
		EV Charger DSR
		EV Charger V2G
		Flexible Site Demand	(Flexible Site Demand) Fixed Reference

Table 3: DBMs for I&C DER

Asset Scale	Metering Arrangement	Technology Type	DTD / GTU	DTU / GTD
I&C	Asset Level	Schedulable Generation	Zero	Nomination
		Intermittent Generation	Zero	Nomination
		Storage	Zero
		Heat Pump	Nomination
		EV Charger DSR
		EV Charger V2G
		Flexible Site Demand
	Point of Connection	Schedulable Generation
		Intermittent Generation
		Storage
		Heat Pump
		EV Charger DSR
		EV Charger V2G
		Flexible Site Demand

The DBM should be allocated at the point of registration.

NOTE: Where a DER has different default methodologies depending on the direction of the service (i.e. DTD/GTU or DTU/GTD), all relevant options should be listed, and at the point of bidding for a service, where the relevant direction is known, the specific default methodology will be confirmed.

Where a DNO allows Planned Assets (such as DERs that are currently under development or an intention of an FSP to recruit third-party DERs in the future) to be bid into their flexibility markets, the FSP may not have all the information required for the DBM to be allocated at the point of bid submission. Under this scenario, no DBM will be allocated, but as part of the Development Plan that would be agreed between the DNO and the FSP, a deadline for the DBM process to be completed before the first contracted service period will be agreed.

GuidanceGuidance: Mapping of the Energy Source/Technology Types used in the Pre-Qualification Criteria to the technology types in this document

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.

The following mappings apply:

Energy Source/Technology Type	Consolidated Baselining Category
Advanced Fuel (produced via gasification or pyrolysis of biofuel or waste)	Schedulable Generation
Biofuel – Biogas from anaerobic digestion (excluding landfill & sewage)
Biofuel – Landfill gas
Biofuel – Other
Biofuel – Sewage gas
Biomass
Fossil – Brown coal/lignite
Fossil – Coal gas
Fossil – Gas
Fossil – Hard coal
Fossil – Oil
Fossil – Oil shale
Fossil – Other
Fossil – Peat
Geothermal
Hydrogen
Nuclear
Waste
Solar	Intermittent Generation
Water (flowing water or head of water)
Wind
Stored Energy (all stored energy irrespective of the original energy source)	Storage
Onsite Battery	Storage
Air Source Heat Pump	Heat Pump
Ground Source Heat Pump
Water Source Heat Pump
Hybrid Heat Pump
EV Charger DSR	EV Charger DSR
EV Charger V2G	EV Charger V2G
Flexible Site Demand	Flexible Site Demand

2.3Alternative and Confirmed Baselining Methodologies

An Alternative Baselining Methodology (ABM) is available to ensure that DERs with atypical characteristics or operational behaviours can be fairly and appropriately assessed where the DBM is not suitable. The only option for an ABM is a Nomination baseline. Further details are set out in later sections.

A high-level overview of the ABM request process and how it leads to the Confirmed Baselining Methodology (CBM) is shown below:

The CBM shall be used for all verification and settlement calculations.

By the implementation deadline of this Flexibility Marker Rule, DNOs will begin publishing the key deadlines for:

confirming the allocated DBM
the latest point at which an FSP can raise an ABM request
when the CBM will be confirmed by the DNO.

NOTE: While it is anticipated that in the majority of cases that once the CBM notification deadline passes, there should be no further changes to the applicable baselining methodology for a Meterable Unit, there may be certain cases where this is an appropriate action. In such cases, either the DNO or the FSP may propose a change to the CBM after the standard deadline, which will be implemented if agreed by both parties.

NOTE: Following notification from a DNO of ABM approval, the platform provider will override the DBM allocated to the specific DER based on an approved use of the ABM for a specific group of DER(s) within a Meterable Unit. This ABM allocation should be the enduring position rather than time limited.

2.4Aggregation of DERs into Meterable Units

Baselining will be completed at a Meterable Unit level rather than individual DER level. A Meterable Unit is the aggregated level used for settlement and may consist of either multiple DERs or a single DER, as shown in the examples below:

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The following controls will be implemented:

Non-Nomination baselined DERs (using the baselines of Asset Capacity, Zero or Fixed Reference) can be grouped into a single Meterable Unit, as all methodologies make use of static values, which are known in advance and are set by DNOs.
Non-Nomination baselined DERs cannot be grouped into a Meterable Unit containing Nomination baselined DERs, as Nomination baselines use values which are submitted by the FSP and therefore, a Meterable Unit containing Nomination baselined DERs are subject to accuracy standards.
If an FSP wishes to combine Non-Nomination baselined DERs with Nomination baselined DERs into a Meterable Unit, the FSP would be required to submit an ABM request (see next section) to the DNO for all Non-Nomination baselined DERs to become Nomination baselined.

NOTE: Where a DER has an option for the DBM used dependent on the direction of the service (i.e. DTD/GTU or DTU/GTD), care must be taken in grouping applicable DERs into a Meterable Unit. For example, I&C DBMs metered at Asset Level for Schedulable Generation or Intermittent Generation have a DTD/GTU methodology of “Zero” but a DTU/GTD methodology of “Nomination”. This means that this particular variant of DER could be grouped into different Meterable Units (i.e. Nomination or Non-Nomination) depending on which direction the service is for.

GuidanceExplainer: What does aggregation into a Meterable Unit look like in practice?

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.

A simplified example for two scenarios is provided in this section. These examples are non-exhaustive and do not cover all circumstances where they would be used (e.g. combining other types of asset or multiples of the same asset type).

Example - For the grouping of Non-Nomination Baselined DERs into a Meterable Unit. It requires the aggregation of the static baseline values.

In the example, the technology types involved are a Heat Pump and Storage. In both cases, they are installed at a domestic site, the metering arrangement used is Point of Connection, and the service direction is DTD/GTU. From the table for the overview of DBMs for domestic sites (Table 2) the relevant baseline methodology in this case is the Zero plus Fixed Reference baseline for Flexible Site Demand to be used for the Point of Connection metered Storage DER, while the Point of Connection metered Heat Pump DER calls for the Heat Pump Fixed Reference and Flexible Site Demand to be used.

In this example, the Heat Pump and Storage DERs are located in the same domestic property. Therefore, the Fixed Reference value for the Flexible Site Demand is only used once in the baseline values. If these DERs were located at separate domestic properties, the Flexible Site Demand would be included twice to reflect this.

The diagram below illustrates how this would work in practice and, using the indicative figures, would result in a baseline value of -2.75 kW for the property and Meterable Unit.

NOTE: Note kW values shown are for illustration purposes only

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.

Taking a second example: the technology types involved are a Heat Pump and an EV Charger DSR. In both cases, they are installed at a domestic site, the metering arrangement used is Point of Connection, and the service direction is DTD/GTU. From the table for the overview of DBMs (Table 2) for domestic sites the relevant baseline methodology in this case is the EV Charger Fixed Reference baseline and Flexible Site Demand to be used for the Point of Connection metered EV Charger DSR DER while the Point of Connection metered Heat Pump DER calls for the Heat Pump Fixed Reference and Flexible Site Demand to be used.

Again, in this example, the Heat Pump and EV Charger DSR DERs are located in the same domestic property. Therefore, the Fixed Reference value for the Flexible Site Demand is only used once in the baseline values. If these DERs were located at separate domestic properties, the Flexible Site Demand would be included twice to reflect this.

The diagram below illustrates how this would work in practice and, using the indicative figures, would result in a baseline value of -4 kW for the property and Meterable Unit.

NOTE: Note kW values shown are for illustration purposes only

2.5Alternative and Confirmed Baselining Methodologies

DNOs shall independently calculate and set their Fixed Reference Baselines.

To provide better visibility of these calculations, DNOs shall submit Reference Data, containing their Fixed Reference Baselines for each distinct categorisation to the Market Facilitator.

2.6Nomination Baselining Requirements

2.6.1

Nomination Baselining Methodology Submission Deadline

For any Meterable Unit where a Nomination baseline is the CBM, the FSP must submit a Nomination to the DNO no later than the bid submission deadline during the flexibility services tender process. This ensures that, should the FSP be issued a contract award notice, the DNO will already hold a valid nomination value that can be used as a fallback for settlement purposes if no updated Nomination is received before the first flexibility service period.

NOTE: Where there may be a significant gap between contract award notice and service delivery (e.g. in the case of long-term tenders), the expected behaviour of a Meterable Unit may change over time (e.g. changes may arise due to portfolio churn within the Meterable Unit or improvements in forecast accuracy closer to delivery). To mitigate this, FSPs will have the ability to resubmit updated Nominations beyond the original bid submission deadline, where appropriate.

NOTE: For any flexibility products where the Utilisation Instruction Timing is set at the point of trade, meaning that upon receiving a contract award notice, the FSP has certainty that flexibility delivery will be required in the awarded service period (e.g. Peak Reduction and Scheduled Utilisation products). Allowing unrestricted Nomination resubmissions after contract award introduces a material risk of gaming, as there is no opportunity to verify the FSP’s nomination against typical operating behaviour. As such, for these products, the Standard Resubmission Deadline is also the bid submission deadline. Nonetheless, provisions have been established to enable post-deadline nomination resubmissions in exceptional circumstances, subject to DNO approval.

Details of the deadlines for nomination submissions are shown in Table 4 below.

Table 4: Deadlines for Nomination baseline methodology submissions

Product Type	Utilisation Instruction Timings	Nomination Type
Product Type	Utilisation Instruction Timings	1st Submission	Standard Resubmission Deadline	Extended Resubmission Deadline
Peak Reduction	At trade	Bid Submission Deadline	Bid Submission Deadline	Day-1, 12:00
Scheduled Utilisation	At trade		Bid Submission Deadline
Operational Utilisation (including Scheduled Availability & Variable Availability where applicable)	Week Ahead		Week-1, Thursday 12:00
	Day Ahead		Day-1, 12:00	Day, Hour-1
	15 Minutes		Day, Hour-1	N/A
	2 Minutes		Day, Hour-1	N/A

An FSP may make a request to a DNO for approval to apply the Extended Resubmission Deadline for a Meterable Unit in situations where the Standard Resubmission Deadline has passed, but extenuating circumstances have materially affected the expected behaviour of that Meterable Unit.

Extenuating circumstances may include, but are not limited to:

Outages affecting the Meterable Unit's normal operation
Communication system failures that prevented the timely submission of a Nomination
Demand Control Events
The impact of Event Days from other contracted services
Significant portfolio churn or fundamental changes in the Meterable Unit’s expected behaviour

Upon receiving such a request, the DNO will assess whether the circumstances constitute a valid extenuating event with a material impact and is satisfied that sufficient evidence (where requested) has been provided to determine whether to grant the use of the Extended Resubmission Deadline for the affected Meterable Unit.

2.6.2

Guidance for Nomination Baselining

FSPs shall adhere to the principles outlined below when developing a Nomination baseline. These principles are recognised as good industry practice.

Consistency: Nominations should be based on a stable and repeatable methodology that does not change arbitrarily between events or periods.
Data-driven approach: Where possible, Nominations should be informed by recent historical meter data or justified forecasts aligned to known operational characteristics, including the impacts of factors such as stacking.
Transparency and traceability: The rationale and assumptions behind Nomination values must be clearly documented and made available to the DNO if requested as part of a Nomination Performance Review.
Forward-looking basis: Nominations should reflect expected behaviour in the nominated period, not be retroactively adjusted based on past performance.
Auditability: The methodology used to generate nominations must be capable of independent verification by the DNO as part of a Nomination Performance Review.

2.6.3

Nomination Baselining Justification

Justification of the Nomination baseline should be submitted by FSPs to DNOs in a concise manner.

The process map below provides a high-level overview of how the Nomination justification and accuracy process should operate.

In most cases, where a consistent methodology is used, FSPs should be able to reuse their justifications across events with no or minimal change. Only in situations where unique or time-sensitive conditions have affected the Nomination, such as operational constraints or the influence of revenue stacking, would a more specific explanation be required.

In accordance with principles outlined above (i.e. good industry practice), the justification for a Nomination baseline developed by an FSP should address the following questions:

Consistency

What methodology have you used to calculate the Nomination?
Has this methodology been applied consistently across other events or periods? If not, why not?

Data-Driven Approach

What data sources (e.g. historical meter data, forecasts, control system outputs) informed your Nomination?
How have you accounted for known operational factors, including the impact of revenue stacking?

Transparency and Traceability

What are the key assumptions behind your nominated value?
Where are these assumptions and data sources documented for reference?

Forward-Looking Basis

How does the Nomination reflect expected behaviour during the nominated period?
If it differs from recent historic usage, what justifies the change?

Auditability

Can you provide supporting evidence (e.g. data files, forecast models, internal approval records) if requested?
Is the nomination process traceable and verifiable by an independent reviewer?

NOTE: FSPs can submit a standardised justification statement, rather than a submission for each nomination, for scenarios where the asset and site operating conditions allow the principle of consistency to be met. This approach shall be agreed with the relevant DSO.

2.6.4

Nomination Baselining Methodology Accuracy

Accuracy assessments will be completed on a quarterly basis for each calendar month by the DNO, and the results will be reported to the Market Facilitator as per section 3.

The accuracy calculation assessment has been designed to account for the maximum usable swing in either direction (import to export and vice versa), constrained by any declared operational limitations (the Available Capacity), and assesses error levels in proportion to the Meterable Unit’s capacity, to ensure the measure reflects the relative scale of the Meterable Unit.

These will be assessed against the Net % Error and the Absolute % Error.

Net % Error – Identify, over an assessment period, the average net error of a Meterable Unit to highlight whether on average, a Meterable Unit’s behaviour is consistently over or under an FSP’s Nomination values

Absolute % Error – Identify performance of a Meterable Unit over an assessment period in absolute terms to mitigate the risk of positive and negative Net % Errors netting to give a false indication of accurate Nominations. The absolute error assessment provides a clear indication of accuracy over an assessment period.

Where Effective Capacity is:

The terms used in the formulae are defined in Table 5.

Table 5: Variable terms definitions

Variable	Description
u	The Meterable Unit being assessed.
m	The month being analysed.
s ∈ S(m)	Each settlement period “s” within the month “m”
Nominationᵤ,ₛ	The Nomination submitted by the FSP for the Meterable Unit in MW at time “s”
Metered Outputᵤ,ₛ	The metered value in MW at time “s”
Import Capacityᵤ,ₛ	The fully rated import capacity of the Meterable Unit in MW at time “s”
Export Capacityᵤ,ₛ	The fully rated export capacity of the Meterable Unit in MW at time “s”
Available Capacityᵤ,ₛ	The declared available capacity for the Meterable Unit at time “s”

Thresholds, for the measures will be set by the DNOs, in alignment with the standard values set out in Section 3. Upon failure to meet these thresholds, the DNO will have the right to initiate a Nomination Performance Review. These thresholds may be updated in a future revision of this Flexibility Market Rule following data analysis on actual performance data.

GuidanceExplainer: What data is used in the Net % Error and Absolute % Error calculation?

The calculation is based on using data where the contracted asset has not been dispatched for a period within a contracted service window. Taking an example to illustrate this, where the contracted service window is between 16:00 and 18:00 for two days and the service is being delivered by an asset that has a Nomination Baseline.

Day #1 – service is dispatched – meter reads for the full 2-hour service window are provided by the FSP to the DNO - These are used for settlement against the nominated baseline value.
Day #2 – service is not dispatched – meter reads for the full 2-hour service window are provided by the FSP to the DNO – The DNO can then use these meter reads to directly compare to the nominated baseline values, enabling a full analysis of the accuracy of the nomination, without a dispatch event skewing the behaviour.

The Day #2 data is what would be used in the calculation of Net % Error and Absolute % Error for that month. Day #1 data, where the service is dispatched, is only used for settlement purposes.

Event Days should be excluded from the calculation, as this skews the accuracy. In the example, if on Day #2 the service isn't dispatched by the DNO and the FSP knows it isn't going to be utilised and can use the asset for a NESO service this would qualify as an Event Day, one option is to allow the use of the Extended Resubmission Deadline (allows for an FSP to extend the time period that they can re-submit nominations with one of those listed in section 2.6 Table 4, valid reason being the impact from Event Days from other contracted services).

The other option is to account for it under the Nomination Performance Review, where Stage 1 allows that 'the FSP may submit additional information to the DNO to provide any mitigation that explains the cause for the accuracy standards not being adhered to'. This could also cover the scenario where the FSP did breach the thresholds for responding to a dispatch that had been received after the Extended Resubmission Deadline.

Where there are no days that are not Event Days there would be no data available for the Net % Error or Absolute % Error calculations, so the DNO wouldn't be expected to run the calculations. In this scenario where all service windows have been dispatched, this is where the nomination justification would be used. As there isn't a period that allows a direct observation of normal behaviour, the DNO instead would use the nomination justification as the basis for an assurance technique for the assessment.

GuidanceExample: Nomination Baseline Accuracy

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.

The following example for a Battery Energy Storage System (BESS) operating bi-directionally over the assessment period illustrates how the assessment of accuracy would work in practice.

In the example, there are five periods under consideration (Table 6 s1 to s5) and the standard sign convention of export being a positive value and import being a negative value has been used.

Table 6: Example data

Interval	Nomination (MW)	Metered Output (MW)	Import Capacity (MW)	Export Capacity (MW)	Available Capacity (MW)
s1	-3	-5	-5	5	-4
s2	2.5	1	-5	5	-6
s3	-1	1	-5	5	-3
s4	3	2.5	-5	5	-5
s5	-2	-1.5	-5	5	-2.5

NOTE: The Available Capacity covers any swing from import to export, or vice versa, where the technology type has that capability. For example, in the table above, the Available Capacity for period s2 is -6MW and this could be a GTD of 2.5MW and a DTU of 3.5MW.

The Nomination (MW) less Metered Output (MW) for each period is aggregated to give a total of 1.5MW of the net error calculation. The absolute value of Nomination (MW) less Metered Output (MW) for each period is aggregated to give a total of 6.5MW of the absolute error calculation.

Table 7: Aggregated net and absolute value of Nomination (MW) less Metered Output (MW) for s1 to s5

Interval	Nomination (MW) – [A]	Metered Output (MW) – [B]	Aggregate net value [A] – [B] (MW)	Aggregate Absolute value ABS([A] – [B] (MW)
s1	-3	-5	2	2
s2	2.5	1	1.5	1.5
s3	-1	1	-2	2
s4	3	2.5	0.5	0.5
s5	-2	-1.5	-0.5	0.5
TOTAL			1.5	6.5

The aggregated Effective Capacity is -19.5MW (Table 8).

Table 8: Aggregated Effective Capacity for s1 to s5

Interval	Import Capacity (MW) – [A]	Export Capacity (MW) – [B]	Available Capacity (MW) – [C]	Min (Max(\|A\|, \|B\|), \|C\|) (MW)
s1	-5	5	-4	4
s2	-5	5	-6	5
s3	-5	5	-3	3
s4	-5	5	-5	5
s5	-5	5	-2.5	2.5
TOTAL				19.5

This gives a Net % Error of 7.69% (i.e. 1.5MW / 19.5MW) and an Absolute % Error of 33.3% (i.e. 6.5MW / 19.5MW).

2.6.5

Nomination Performance Reviews

Where an FSP is not meeting the accuracy performance requirements (i.e. Net % Error and/or Absolute % Error) for a Nomination baseline, a DNO has the right to initiate a Nomination Performance Review. There are three possible stages to the process:

Stage 1: Nomination Performance Review

The DNO will notify the FSP where accuracy standards have not been met. The notification will include the identifier for the Meterable Unit(s), the assessment period and, as applicable, the calculated Net % Error and/or Absolute % Error figures.
The FSP may submit additional information to the DNO to provide any mitigation that explains the cause for the accuracy standards not being adhered to. The information shall demonstrate that the FSP was acting in accordance with the principles of good industry practice as defined in this Flexibility Market Rule and, if applicable, details of a reasonably unforeseeable circumstance which caused the accuracy standards to be exceeded.
If the DNO is satisfied that the principles of good industry practice have been followed, then no further action will be taken, and the FSP may continue participating as normal.

Stage 2: Advanced Monitoring Stage

If the DNO is not satisfied that the FSP demonstrated adherence to the principles of good industry practice during the initial stage of the performance review or that there was a reasonably unforeseeable circumstance which caused the accuracy standards to be exceeded, the DNO will place the Meterable Unit under Advanced Monitoring.
During this period, the FSP will be expected to improve both accuracy performance and compliance with the principles of good industry practice, with more frequent reviews (i.e. more frequently than quarterly).

Stage 3: Removal from Flexibility Services

If, during the Advanced Monitoring stage, the FSP continues to fail to meet the required accuracy thresholds and fails to demonstrate any improvement in either performance or alignment with the principles of good industry practice, the DNO may, at their sole discretion, terminate the contract for flexibility services relating to the affected Meterable Unit(s).

3Market Information

3.1Implementation tracking

The DNOs must provide the Market Facilitator with the data set out in Table 9. The data provided should accurately reflect their implementation of the rule.

The expected values required for compliance are also set out in Table 9.

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 9: Implementation tracking requirements

FMR-SBM	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-SBM

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 DNOs must update the Market Facilitator with the data set out in Table 10 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 10.

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.

DNOs shall also publish this information themselves.

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

Table 10: Flexibility Market Catalogue data

Parameter	Description	Required Value
Baselining	Summary of the baselining approach used	As per Standard Baselining Methodology
Maximum allowable Net % error for nomination baselines	Maximum error allowed in the Accuracy methodology before performance reviews are kicked off	10%
Maximum allowable Absolute % error for nomination baselines	Maximum error allowed in the Accuracy methodology before performance reviews are kicked off	20%

3.3Effectiveness monitoring

The following metrics shall be used to assess the effectiveness of the rule.

The DNOs must provide the Market Facilitator with any Additional Input Data as set out in Table 11 below for element in scope of this rule. The data provided should accurately reflect their implementation of the rule.

The expected values and the minimum required values for compliance, if any, are also set out in Table 11.

Initial Additional Input Data shall be sent as reasonably practical following the first quarter of implementation of this Flexibility Market Rule.

Additional Input Data shall be sent in accordance with the Cadence set out in Table 11.

Updates to Additional Input Data 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 11: Effectiveness monitoring metrics

Metric 1	Description	Number of ABM requests approved
	Why are we tracking this?	To validate the effectiveness of the DBM. A high volume of ABM requests could highlight an issue with a particular DBM(s) that would require further analysis and potential amendment in a subsequent version of this rule.
	Cadence	Quarterly
	Data Source	Existing Data - Additional Input Data – Number of ABM requests approved in the last quarter
	What does good look like?	Low volumes
	Minimum Requirement
Metric 2	Description	Average Nomination Baselining Net % Error for a Meterable Unit
	Why are we tracking this?	To validate the effectiveness of the Nomination Baseline calculation by an FSP for a Meterable Unit. A high Net % Error figure could highlight an issue with a particular FSP or Meterable Unit in their procedures for determining a Nomination Baseline. It will also be used to determine if the limits, as specified in Table 12 are at the correct level. This would inform further analysis and potential amendment in a subsequent version of this rule.
	Cadence	Quarterly
	Data Source	Existing Data - Additional Input Data – Average (monthly) Net % Error figures per Meterable Unit over the last quarter
	What does good look like?	Low percentage
	Minimum Requirement
Metric 3	Description	Average Nomination Baselining Absolute % Error for a Meterable Unit
	Why are we tracking this?	To validate the effectiveness of the Nomination Baseline calculation by an FSP for a Meterable Unit. A high Absolute % Error figure could highlight an issue with a particular FSP or Meterable Unit in their procedures for determining a Nomination Baseline. It will also be used to determine if the limits, as specified in Table 12 are at the correct level. This would inform further analysis and potential amendment in a subsequent version of this rule.
	Cadence	Quarterly
	Data Source	Existing Data - Additional Input Data – Average (monthly) Absolute % Error figures per Meterable Unit over the last quarter
	What does good look like?	Low percentage
	Minimum Requirement
Metric 4	Description	Number of Nomination Performance Reviews
	Why are we tracking this?	To validate the effectiveness of the Nomination Baseline procedures of an FSP. A high number of reviews could highlight an issue with a particular FSP or Meterable Unit in their procedures for determining a Nomination Baseline.
	Cadence	Quarterly
	Data Source	Existing Data - Additional Input Data – Number of Nomination Performance Reviews in the last quarter
	What does good look like?	Low volumes
	Minimum Requirement

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.

Glossary

Term	Aliases	Definition
Absolute % Error	-	Means, over an assessment period, the calculated average absolute error of a Meterable Unit.
Alternative Baselining Methodology	ABM	a non-DBM baselining approach where the applicable DBM is not suitable due to the DER having atypical characteristics or operational behaviours.
Asset Capacity	-	a baselining technique which assumes the participating DER operates at its full rated capacity during the flexibility event, irrespective of actual operational conditions.
Confirmed Baselining Methodology	CBM	the baselining methodology that will be utilised in the assessment of the performance of the DER. This will either be the relevant DBM, or, where approved by the DNO, the ABM.
Distributed Energy Resource	DER	energy resources comprised of generation and/or storage and/or controllable load, which is connected at the low or medium voltage distribution level.
Default Baselining Methodology	DBM	the baselining methodology that should be applied based on the Location Type, Metering Location, Technology Type and direction of the service (i.e. DTD/GTU or DTU/GTD).
Event Days	-	a day that can be excluded from a Recent History baseline methodology for activities such as delivery of Balancing Services, Virtual Trading, Site Outage, Equipment and/or Site Disconnection occurring on that day.
Fixed Reference	-	a baselining technique which uses a fixed daily profile derived from the observed energy behaviour of a representative group of DERs that represents normal operating behaviour or a DNO’s planning scenarios.
Location Type	-	either a domestic premise or an Industrial & Commercial (I&C) premise.
Meterable Unit	-	an aggregated collection of DERs, or a single DER, that are either all a non-Nomination DBM or all a Nomination DBM.
Metering Location	-	a location for the metering either at the Point of Connection to the Distribution System (i.e. the Boundary Point Metering System) or a behind the Boundary Point Metering System located at the asset providing the flexibility service.
Net % Error	-	Means, over an assessment period, the calculated average net error of a Meterable Unit. A negative net error indicates Nominations are higher than the Meterable Unit’s normal behaviour, while a positive error indicates the Nominations are under the Meterable Unit’s normal behaviour.
Nomination	-	a baselining technique which uses an estimated/expected set of meter values, provided by the Flexibility Services Provider (FSP), based on the expected or normal operation of the site / DER without any flexibility event, for a future availability window that then becomes a utilisation event.
Recent History	-	a baselining technique which uses a set of recent, eligible days (i.e. excluding Event Days such as a day providing a flexibility service) preceding a utilisation event. This may also include correction factors such as within-day adjustments for weather variables or removal of outlier values.
Technology Type	-	the type of Distributed Energy Resource (DER) which is the asset providing the flexibility service. For example, an EV Charger.
Zero	-	a baselining technique where the baseline energy consumption or generation is set to zero, meaning no energy usage or production is assumed in the absence of the utilisation event.

FMR: Standard Baselining Methodologies - 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	Last Updated 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 changes	CP002	CP002
2.1	17/02/2026	Final	Derogation Rule added
2.2	18/03/2026	Final	Derogation Rule added

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-SBM
Title	Standard Baselining Methodologies
Type	Flexibility Market Rule
Collection	Sub-Market Alignment
Audience	DNOs, FSPs, market platform providers
Expertise	Baselining, Performance Management
Owner	Market Facilitator
Expected benefit	Aligned baselining process, reduced variation across DNOs
Related end-to-end process reference	Q11. Register Baseline
References	FMR-SMD, FMR-PD
IsReferencedBy	FMR-SMD
Published version number	2.2
Applicability	All DNO sub-markets
Published Date	04/02/2026
Implementation Date	01/04/2026
End Date	-
Terms of variations	Approved Derogation
IsReplacedBy	N/A
Replaces	N/A
Status	Final
Change since last version	Housekeeping changes – Improvements to Nomination Baselining Methodology Accuracy (text changes and guidance). Update to sections 3.3, Sub-market and technology mapping guidance.
Description	What? This rule sets out the minimum expectation for the use of standardised baselining methodologies in DNO markets. How? The rule defines different types of baselining techniques that should be used in defined criteria/circumstances. It defines the minimum accuracy requirements for Nomination baselines, expectations on following the principles of good industry practice for developing Nomination baselines, escalation routes and enhanced monitoring. It also sets out the requirements for the use of any alternatives to the defined methodologies. It sets out requirements for stakeholders to share/submit information to meet this rule. Who? This rule impacts all DNOs, FSPs and market platform providers. When? This rule comes into force on 01/04/2026 Why? The rule aims to provide a standard approach to the use of baselining methodologies in DNO markets.