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 September 2021: 

  • Gas: 35% 
  • Wind: 28% 
  • Nuclear: 16% 
  • Interconnectors: 11% 

 In September 2021, there was 5,724GWh of Wind generation, the largest monthly Wind generation total since February 2020 (6,451GWh).

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.  


In October, the North Scotland GSP Group (_P) had a positive minimum GSP Group Take just two days. The lowest GSP Group Take in October was –328MWh, occurring on 21 October.

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

This chart shows the daily sum of the SVA Registered Embedded Generation volume for each GSP Group for the day when that GSP experienced the highest volume of Embedded Generation during that month.


In November, seven of the 14 GSP Groups saw a decrease in their maximum GSP Group metered volume supplied by SVA Registered embedded generation compared to September.    

  These seven GSP Groups were:  

  •  Eastern (_A) 
  • East Midlands (_B)  
  • Midlands (_E)  
  • Northern (_F) 
  • North Western (_G) 
  • Southern (_H)  
  • South Western (_L)



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 two regions beyond the threshold variation of +/- 1.5%, South Wales (_K), and Yorkshire (_M). 

The ADR for Eastern is now within the acceptable threshold variance after the GSP metering fault that we feel accounts for the ADR drop was fixed. 

On the upward trend for the ADR in both South Wales and Yorkshire, the investigation is still ongoing. Elexon will continue to update the 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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