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Trading & Settlement

Electricity is traded on a wholesale market, with generators and suppliers entering into contracts with each other for every half hour of every day; sometimes years in advance. Non-physical traders such as a investment banks also participate in this trading. For each half hour – known as a settlement period – they can continue to trade up to 1 hour beforehand. At this point the market for that time period is closed – this is gate closure.

Following gate closure, National Grid uses the balancing mechanism to balance the system. Contract notifications, bids and offers, and other data, is passed to BSC Central Services for imbalance settlement.

BSC Central Services in summary

The following diagram shows the various IT systems used in the imbalance settlement process. Collectively the systems in the shaded blue area are known as the ‘BSC Central Services’. Please click on the diagram to see a full interactive version.


  • Central Registration Agent (CRA) – manages market participant registrations


  • Energy Contract Volume Aggregation Agent (ECVAA) – receives notifications of bilateral contracts
  • Balancing Mechanism – balances the energy on the system (managed by National Grid (NGC))


  • Central Data Collection Agent (CDCA) – collects power station metered volumes (what has been generated)
  • Supplier Volume Allocation Agent (SVAA) – aggregates Supplier metered volumes (what has been consumed)
  • Settlement Administration Agent (SAA) – calculates the cashflows
  • Funds Administration Agent (FAA) – sends out the invoices


  • Balancing Mechanism Reporting Agent (BMRA) – publishes Balancing Mechanism data on the BMRS site
  • Market Index Data Provider (MIDP) – provides Power Exchange pricing data

Contract Notification Guidance

Information and guidance on the processes for managing contract notifications and submitting details to the Energy Contract Volume Aggregation Agent (ECVAA).

ECVAA Web Service Guidance

Settlement Calendars

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.