Generation and Demand data from the Trading Operations Report


The page below details highlighted Generation and Demand data from the previous month. This data is acquired from BSC Agents and inputted to the Trading Operation Monitoring Analysis System (TOMAS) database.

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Sum of CVA Generation by fuel type per settlement date

BM Units that are registered in the Central Volume Allocation arrangements rather than through the Supplier Volume Allocation Arrangements have their metered data collected centrally by the Central Data Collection Agent. A single fuel type is assigned to each BM Unit and the sum of metered volume by fuel type is displayed by Settlement Day.


CVA generation in March 2021:

  • Gas: 42%
  • Wind: 20%
  • Nuclear: 15%
  • Interconnectors: 11% 

The highest daily total generation for all fuel types was 903GWh on 11 February 2021.

Sum of CVA wind generation per settlement date

The graph below displays the wind generation that is registered in CVA only. The sum of metered volume is displayed by Settlement Day. GB wind generation can be registered in the Central Volume Allocation (CVA) arrangements, the Supplier Volume Allocation Arrangements or may not register at all. 


On 28 March 2021, CVA Wind generation was 274GWh, accounting for 47% of all CVA generation on that day.

Minimum GSP Group Take based on SF run

The aim of the charts is to provide timely notification of any GSP Group that could become a net exporting GSP Group. The concern is that the underlying rules in the BSC implicitly assume that GSP Groups will import energy. Any deviation from this assumption results in the rules becoming unstable.

This chart provides a plot of the minimum value of GSP Group Take, (i.e. consumption) at the (Initial Settlement) SF run for each of the GSP Groups in each Settlement Day over the last 3 months. A negative GSP Group Take means the GSP Group is a net exporter.  


North Scotland GSP Group continued to be the only net exporter; on 5 April 2021, North Scotland exported 352MWh, which is the largest amount exported in the region since 16 January 2021 (340MWh).

Maximum GSP Group metered volume supplied by SVA registered embedded generation for each GSP Group

The aim of this graph is to show the total volume of embedded generation. This chart shows the daily sum of the SVA Registered Embedded Generation volume for each GSP Group.


Maximum embedded generation dropped in eleven out of 14 GSP regions in April 2021. The largest drop was in the South Scotland GSP Group, where maximum embedded generation metered volumes dropped from 31GWh in March 2021 to 26GWh in April 2021. The largest increase in Maximum embedded generation was in the Southern GSP Group, where maximum embedded generation metered volumes increased from 14GWh in March 2021 to 15GWh in April 2021.


Annual Demand Ratio Values based on Settlement Run Type R2 or later

The chart below shows the ADR values for each GSP Group on a daily basis. ADR values have been calculated for the year ending on the dates indicated. To achieve the best trade-off between up to date information and accuracy the chart is based on Second Reconciliation (R2) Settlement Run data or from later Settlement Runs if these are available. Trends in the pattern of ADR may indicate issues with metering data within the GSP Groups.


The ADR graph shows three regions beyond the threshold variation of +/- 1.5%: Eastern (_A), South Wales (_K), and Yorkshire (_M).    

Regarding the ADR for Eastern, Elexon can confirm that the GSP metering fault that accounts for the ADR drop has been fixed. Hence, the ADR in this region is gradually rising to normal levels, as the data enters into Settlement through the Settlement Runs.  

On the upward trend for the ADR in both South Wales and Yorkshire, investigation is still ongoing.  Elexon will continue to update industry, and the relevant Elexon committees, on a regular basis, with feedback from committees taken into account in our investigations.  

About Annual Demand Ratio

Annual Demand Ratio provides a high-level understanding of the overall performance of the Non Half Hourly (NHH) Supplier Volume Allocation (SVA) market and identifies any significant under-/over-accounting of energy. Whilst the theoretical ‘ideal’ value of ADR is 1, variations of +/- 1.5% are to be expected due to inaccuracies in line loss estimates and a small usage of estimates at Final Reconciliation (RF) run. Values of less than 1 may result from the over-accounting of import energy in SVA, the under-accounting of export energy in SVA or under-accounting of Grid Supply Point (GSP) metering. Values of greater than 1 may result from the under-accounting of import energy in SVA, the over-accounting of export energy in SVA or over-accounting of GSP metering.


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