The AER has shared a Major Event Day threshold calculation workbook. The workbook illustrates how the Major Event Day threshold can be calculated in line with the 2.5 Beta methodology set out in Appendix D of the STPIS, noting a DNSP may propose an alternate methodology in accordance with clause 2.2 of the STPIS.

On 7 January 2025, AER updated the formula in the Ln(SAIDI) column on advice from CPU. This change will return a null value for Ln(SAIDI) when daily SAIDI is zero as intended by STPIS v2.0.