Credit Assessment Load Factor

Each BM Unit has a Credit Assessment Load Factor (CALF) value or a Supplier Export CALF (SECALF), which is a measure of their average generation/demand as a ratio of their maximum for the current BSC Season. These values are calculated seasonally for each BM Unit, and each Season’s values are published at the beginning of the preceding Season.

CALF and SECALF are used in the Energy Indebtedness calculation along with Generation or Demand Capacity (GC/DC) until II data is available. An exception is for Interconnector BM Units and Generation Units with Credit Qualifying status who instead use Physical Notifications during this period.

Further details on CALF and SECALF and how they are calculated is published in the CALF Guidance Document.

What are the current CALF and SECALF values?

Values for the upcoming Season, current Season, and two previous Seasons are published on the ELEXON Portal.

Each BM Unit, except for Interconnector and Credit Qualifying BM Units, is given a CALF or a SECALF value for each Season. These are calculated based on the BM Unit’s performance in the previous equivalent Season (the Reference Season). For example, the Summer 2013 CALF values were calculated based on performance in Summer 2012. Values for a given Season are calculated and published three months beforehand.

What are Credit Qualifying BM Units?

Under Approved Modification P215 ‘Revised Credit Cover Methodology for Generating BM Units’, some BM Units are classified as Credit Qualifying. These BM Units do not use the normal “CALF x GC/DC” method for calculating Energy Indebtedness, but instead use their Physical Notifications. As a result, they are not allocated a CALF value, but are given a default value for use if they happen to lose this status.

A list of the current Credit Qualifying BM Units are included within the lists of Seasonal CALF values available on the ELEXON Portal.

What is SECALF?

Under Approved Modification P310 ‘Revised Credit Cover for Exporting Supplier BM Units’, non-Credit Qualifying Supplier BM units with a GC greater than zero and a DC of zero will not use the normal “CALF x GC/DC” method for calculating Energy Indebtedness, but instead use SECALF x GC.

How can I request alternative CALF values?

If you are the Lead Party of a BM Unit and you feel the currently assigned CALF value is inappropriate, you can request an alternative value to be calculated. You can ask for a value to be calculated using the Holiday CALF or the Supplier Volume Allocation (SVA) Embedded Generation methodologies, or you can request a CALF appeal. For SECALF you can request an appeal under the same process. Details of each methodology and the forms for requesting them are all listed in the CALF Guidance Document.

Holiday CALF

Suppliers who experience reduced demand during the two Annual Holiday periods of Christmas/New Year and Easter can request a reduced CALF value to reflect this. Requests should be emailed to 10 Working Days before the relevant Season begins. For a list of the Season start and end dates, see the table below, under the Timetable section.

SVA Embedded Generation

Supplier BM Units that are mostly comprised of Embedded Generation can request this methodology to obtain a negative CALF value. If you plan on applying this methodology to a BM Unit, you need to contact us before the appeal deadline below (i.e. the first working day of the month preceding the start of the Season), as a CALF appeal may be required. The forms should be emailed to

CALF Appeals

If you wish to request an alternative CALF/SECALF, and neither of the above methodologies apply, you need to submit a CALF appeal. You must fill in the relevant pro-forma in the CALF Guidance Document, to detail the grounds of your appeal, and submit this to by the first Working Day of the month preceding the start of the Season. These appeals are then presented to the Imbalance Settlement Group (ISG) as a Confidential Paper.


The dates and deadlines for 2018 are below:

Season Appeal Deadline 10WD Deadline Season Begins Season Ends
Winter 2017 01/11/2017 17/11/2017 01/12/2017 28/02/2018
Spring 2018 01/02/2018 15/02/2018 01/03/2018 31/05/2018
Summer 2018 01/05/2018 18/05/2018 01/06/2018 31/08/2018
Autumn 2018 01/08/2018 17/08/2018 01/09/2018 30/11/2018
Winter 2018 01/11/2018 19/11/2018 01/12/2018 28/02/2019

A Newscast article containing the deadlines for each Season is sent out when the values are first published. A further reminder is sent out the week before the main appeal deadline.


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