Imbalance Pricing

Affected Period



Run type

15/11/2018 08:59

Last Updated
15/11/2018 09:00

Dear Participants,


This note is to advise you of a small number of errors recently identified with Imbalance Pricing:


·        A Pricing Dispute was received for the 27/28/29 October 2018. After initial analysis SEMO has determined that there appears to be an error in the calculation of the Imbalance Price. This error appears to be causing a small number of the Bid Offer Prices used in the ranked set to be based on Complex Commercial Offer Data (COD) when they should be based on Simple COD. SEMO is currently carrying out a full materiality assessment of this error, however initial analysis is that it happens infrequently and for a small number of Imbalance Pricing Periods. This impact assessment is currently ongoing.  The initial findings of the assessment are planned to be provided at next week’s Market Operator User Group (MOUG) meeting.  Discussions are also underway with our vendor; of course, the prioritisation or otherwise of any required fix will be informed by the findings of the materiality assessment of the error.

·        Furthermore SEMO has identified an error in the calculation of the Imbalance Price for the 1/2/6/7 November 2018. This error is also subject to a Pricing Dispute for 3-5 November. On these dates SEMO has observed that the expected Quantity Bid Offer Accepted (QBOA) for a unit is not present for certain Imbalance Price Settlement Periods. The analysis of this error is ongoing.  Further information as to the materiality of this error and when a fix can be expected will also be provided at next week’s MOUG.


SEMO is committed to addressing these issues and re-pricing the impacted periods if applicable. As mentioned above, updates will be provided to Participants via the MOUG meetings on the detail of these errors, the progress on the analysis of their materiality and when fixes can be expected.



Market Operations