Balancing and settlement

This page sets out the various areas that are important when understanding the balancing and settlement processes when trading in the GB electricity market.

What happens when infograph

For each half hour, known as a Settlement Period, companies can trade up to 1 hour beforehand that time period is closed. This is known as Gate Closure.

Following Gate Closure, National Grid uses the Balancing Mechanism to balance the system. Contract notifications, bids and offers, and other data, is sent to BSC Central Services for Imbalance Settlement.

Settlement Calendars and Settlement Periods

There are several Settlement Calendars covering the various Settlement Systems. Visit the Elexon Portal to search these Settlement Calendars for particular Settlement or Agent Run dates or to download a full copy.

Settlement Calendars

There are several Settlement Calendars covering the various Settlement Systems. Use our Portal to search and download these Settlement Calendars for particular Settlement or Agent Run dates.

Settlement Periods

For the purposes of trading and settlement, electricity is considered to be generated, transported, delivered and used in half hour chunks called Settlement Periods.

Settlement Periods are always based on local time. Period 1 is always 0000hrs (midnight) local time. A Normal Day has 48 Settlement Periods, whereas a Short Day (clocks go forward) has 46 and a Long Day (clocks go back) has 50. A conversion table between Settlement Period and Local/GMT Time is shown below:

SETTLEMENT PERIOD

WINTER

SHORT DAY

SUMMER

LONG DAY

GMT

GMT

BST

GMT

BST

BST

GMT

1

0000

0000

 

2300

0000

0000

2300

2

0030

0030

 

2330

0030

0030

2330

3

0100

0100

0200

0000

0100

0100

0000

4

0130

0130

0230

0030

0130

0130

0030

5

0200

0200

0300

0100

0200

0200

0100

7

0300

0300

0400

0200

0300

 

0200

9

0400

0400

0500

0300

0400

 

0300

 

41

2000

2000

2100

1900

2000

 

1900

43

2100

2100

2200

2000

2100

 

2000

45

2200

2200

2300

2100

2200

 

2100

47

2300

 

 

2200

2300

 

2200

48

2330

 

 

2230

2330

 

2230

49

 

 

 

 

 

 

2300

50

 

 

 

 

 

 

2330

GSP Group Correction Factors

GSP Group Correction Factors (GGCFs) are used to ensure that the total energy allocated to Suppliers in each Settlement Period in each GSP Group matches the energy entering the GSP Groups from the transmission system, adjoining GSP Groups and through embedded generation.

Imbalance Pricing

The Imbalance Price is used to settle energy imbalance volumes. At the end of a Settlement Period, BSC Systems compare a Party’s contracted (traded) volume with the metered volume of energy used in the Settlement Period. If a Party is in imbalance of its contracted volume, then it will be subject to imbalance charges.

Trading Charges

Each Trading Party is liable to pay or receive Trading Charges for each Settlement Day. These charges are calculated in relation to Imbalance Settlement and Balancing Mechanism activity. The Settlement Administration Agent (SAA) determines the trading charges.

Maintaining Credit Cover

The purpose of Credit Cover is to ensure that, should a Trading Party default, sufficient collateral is available to pay any debts. If a Party does not have sufficient funds it will enter into Credit Default.

Transmission Losses

Losses on the Transmission System are allocated across BSC Parties through the use of Transmission Loss Multipliers (TLMs). Transmission Loss Factors exist for each TLF Zone (aligning with the existing Grid Supply Point Groups) for each BSC Season in order to allocate transmission losses on a geographical basis.

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