BSC Section Q: Balancing Mechanism Activities

Page type: primary-anchored (mirrors BSC Section Q, Elexon)

Last updated: 5 April 2026 | Section version: v47.0, effective 26 June 2025

Parent page: Balancing and Settlement Code

Section Q governs the real-time balancing market. It covers how Lead Parties submit physical data for their BM Units, how they offer flexibility via Bid-Offer Pairs, and how NETSO accepts those Bids and Offers to keep supply and demand in balance.

1. Introduction

1.1 Scope

Section Q provides for (Q1.1.1): - Submission of BM Unit data per the Grid Code - Physical Notifications enabling Final Physical Notification Data submission - Bid-Offer Pairs and acceptance arrangements - Balancing Services Adjustment Data (BSAD) - Transparency Regulation Data - Loss of Load Probability (LOLP) values - Replacement Reserve Bid arrangements

1.3 Data Submission by NETSO

NETSO submits specified data to the SAA and BMRA for settlement and reporting purposes. (Q1.3)

2. Data Submission by Lead Party

2.1 Dynamic Data Sets

Lead Parties submit operational parameters for their BM Units per Grid Code requirements. These include run-up rates, run-down rates, notice to deviate from zero, minimum stable export/import levels, and other technical characteristics. (Q2.1)

2.2 Maximum Export Limits and Maximum Import Limits

Lead Parties submit MEL (Maximum Export Limit) and MIL (Maximum Import Limit) for each BM Unit. These define the upper bounds on what a unit can deliver or consume. (Q2.2)

3. Final Physical Notification Submissions

3.1 Application

Specifies which BM Units may submit Final Physical Notifications. (Q3.1)

3.2 Final Physical Notification Data

Lead Parties submit FPN data specifying the expected MW output/consumption profile for each BM Unit in each settlement period. This is the baseline against which imbalances are measured. If a generator's FPN says 500 MW and it actually delivers 480 MW, the 20 MW shortfall is imbalance. (Q3.2)

4. Balancing Services Bid-Offer Submission

4.1 Bid-Offer Pairs

Lead Parties submit Bid-Offer Pairs specifying (Q4.1): - Offer price (£/MWh): the price at which the BM Unit is willing to increase output (or decrease consumption) above its FPN level - Bid price (£/MWh): the price at which the BM Unit is willing to decrease output (or increase consumption) below its FPN level - Volume (MW): the quantity available at each price

Multiple pairs may be submitted for each BM Unit, creating a stepped supply/demand curve.

4.2 Balancing Mechanism Default Data

Where Lead Parties do not submit Bid-Offer data, default values apply. (Q4.2)

4.3 Replacement Reserve Bid Data Submission and Default Data

Lead Parties may submit Replacement Reserve Bid data and associated default data. This supports the EBGL Replacement Reserve arrangements. (Q4.3)

5. Balancing Mechanism Bid-Offer Acceptance

5.1 Bid-Offer Acceptances

NETSO accepts Bids and Offers in real-time to balance the system. Each acceptance instructs a BM Unit to deviate from its FPN. These acceptances create the Balancing Mechanism volumes that feed directly into the settlement calculation (Section T). (Q5.1)

5.2 Data Consistency Requirements

Requirements ensuring consistency between acceptance data and the submitted bid-offer data. (Q5.2)

5.3 Acceptance Data

Each Bid-Offer Acceptance notification specifies the volume, timing, and identification data for the acceptance. This data flows to the SAA for settlement and to the BMRA for reporting on the BMRS. (Q5.3)

How it all fits together

The settlement data flow through Section Q:

1. Before gate closure: Lead Parties submit Dynamic Data Sets, MEL/MIL, FPNs, and Bid-Offer Pairs
2. In real-time: NETSO reviews system balance and accepts Bids/Offers as needed
3. After the event: Acceptance data flows to SAA; FPN data provides the baseline; the difference between accepted volumes and FPN is the BM Unit's contribution to balancing
4. In settlement (Section T): BM Unit cashflows are calculated from accepted bid/offer volumes at the submitted prices; residual imbalance is priced at the System Price

Cross-references