Generation and Demand Capacity

Each BM Unit has a Generation Capacity (GC) and a Demand Capacity (DC). This is the maximum expected net Generation and Demand for that BM Unit in the current BSC Season.

These values are declared seasonally. Parties can make resubmissions during the Season if they breach these declared values.

GC/DC is used to calculate whether a BM Unit is a Production (P) or a Consumption (C) BM Unit, which determines which Energy Account that BM Unit’s Metered Volumes are allocated to. If BM Units form a Trading Unit, the GC/DC values are used to determine the P/C Flag for all the BM Units in the Trading Unit. For most BM Units, GC/DC is also used with Credit Assessment Load Factor (CALF) in the Energy Indebtedness calculation until II data is available.

When should I declare GC/DC values?

Initial Registration: When you register a BM Unit, you will register its GC and DC values for that Season as part of that process.

Seasonal Declarations: You need to declare your values for each subsequent Season before they start, with the deadline being ten Working Days before the Season begins. If you do not submit your values by this time, you will be in Default of the BSC.

Mid-Season Re-declarations: All BM Units can opt to re-declare their GC or DC values upward in magnitude at any point during a Season. You need to re-declare your values for a BM Unit if it breaches the current ones. Supplier (2_) BM Units can also opt to re-declare their DC values downward in magnitude during a Season, and this can be done twice per BM Unit in any Season.

When is the deadline for submitting the next Season’s values?

The deadline for submitting a Season’s GC/DC values is ten Working Days before the start of the season. You can still change your values with a mid-Season re-submission, but you will only be able to increase the values in magnitude, except for Supplier BM Units, where it is possible to decrease the magnitude of the DC value.

The dates and deadlines for 2017-2018 are given below:


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


How do I declare GC/DC values?

Seasonal declarations are done using form BSCP15/4.3, and mid-Season re-declarations are done using form BSCP15/4.4 found here on the BSCPs page. These forms should be sent to the Central Registration Agent (CRA) either by email to mailto:[email protected] or by fax to 0870 833 5601.

You need to be a Category A or F Authorised Signatory to submit these forms. For more information about Authorised Signatories, please see BSCP38 ‘Authorisations’.

What could be the impact of re-declaring GC/DC?

If you re-declare GC or DC then this may result in a change of the BM Unit’s P/C Flag. If the BM Unit is a part of a Trading Unit, then the Flag of all the BM Units in the Trading Unit may be affected. This would affect which Energy Account the BM Unit’s Metered Volumes are allocated to, and if this were to change, any Metered Volume Reallocation Notifications (MVRNs) associated with that BM Unit would be automatically end-dated the day before the Flag would change.

If the GC or DC value is used as part of the Energy Indebtedness calculation, you should also be aware of how this might affect your Credit Cover. If the Capacity increases in magnitude, you may find your Indebtedness will go up once that enters the calculation.

What happens if I breach my GC/DC values?

During each Season, we run checks on all BM Units to see if they have breached their GC or DC values. For any BM Units that have, we send the Party an email asking them to re-declare their values accordingly. Any Party that breaches should re-declare their values as soon as possible, otherwise they risk being in breach of the BSC.

There is a tolerance on the size of a breach, and we won’t ask you to re-declare if your breach is within this tolerance. These tolerances are (in magnitude):

  • 2MW if the Capacity is less than 100MW;
  • 2% of the Capacity if the Capacity is between 100MW and 500MW; or
  • 10MW if the Capacity is greater than 500MW.

This is illustrated below:

Tolerance Graph


Where can I get more information?

The current GC and DC values for all BM Units can be found in the Registered BM Unit spreadsheet on the ELEXON Portal.


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