In December 2016, we published the Transmission Pricing Methodology (TPM) – Second Issues Paper Supplementary Consultation document. Appendix F of that paper contained indicative estimates of transmission charges under a proposed new TPM.

Concept Consulting (which undertook the modelling of charges) has recently advised that there was a calculation error that affected some results. This involved the omission of some input data for one scenario.

Consequently, we have provided a corrected version of Appendix F. In addition, an updated set of estimated charges is set out in the document below, which shows the changes from correcting for the error. We have also provided an updated modelling spreadsheet. For most customers, there is relatively little (or no) change to their estimated charges. The impact of the error is within what could be expected under an alternative, but valid application of the same TPM guidelines.

As with the transmission charge estimates in the December 2016 paper, the revised estimates are based on assumptions and simplifications in some areas, and should therefore be treated as broadly indicative only.

While the updated charge estimates are similar to those published previously (and remain indicative in nature), we are releasing them to ensure transparency around estimated financial impacts.