Application by EnergyAustralia and Others

The matter before the Tribunal involved a dispute between TransGrid and the Australian Energy Regulator (AER) over the reasonable operating expenditure (opex) forecast for defect maintenance of new growth assets. The dispute arose in the context of regulatory proceedings concerning TransGrid's asset base and the methodology used to determine its opex forecast. The Tribunal was tasked with reviewing the AER's draft decision that proposed adjustments to TransGrid's opex forecast for defect maintenance of new growth assets, and TransGrid's subsequent revised regulatory proposal.

The key legal issues before the Tribunal were whether the AER was correct in reducing TransGrid's forecast opex for defect maintenance of new growth assets and whether TransGrid's modelling and assumptions regarding its asset base and defect rates were reasonable. Specifically, the Tribunal had to determine if the significant increase in TransGrid's capital expenditure (capex) would skew the model's asset growth input and impact the reasonableness of the opex forecasts, as suggested by the AER based on the advice of PricewaterhouseCoopers (PB).

The Tribunal found that the AER's decision to reduce TransGrid's forecast opex for defect maintenance of new growth assets was not justified. The Tribunal accepted that the average age of TransGrid's assets was increasing and that its asset base was growing and maturing. The Tribunal noted that the AER's focus on new growth assets ignored the broader ageing of TransGrid's system, which would result in higher defect rates due to end-of-life issues. The Tribunal also found that TransGrid's modelling and assumptions were prudent and efficient, based on historical defect rates and the impact of the proposed capital investment program on the average age of its asset types. The Tribunal concluded that the defect rates in the next regulatory period would be higher than in the base year and that TransGrid's assumption of a constant defect ratio may be conservative.

The Tribunal ultimately ruled in favour of TransGrid, stating that there was no reasonable basis for the AER to reduce its forecast opex for defect maintenance of new growth assets. The Tribunal's decision was based on the evidence that the average age of TransGrid's asset base would remain reasonably stable, and that the inclusion of new growth assets would not significantly alter the defect rates. The Tribunal accepted that TransGrid's modelling was based on historical defect rates and that the proposed capital investment program would not materially alter the average age of any asset type. The Tribunal found that TransGrid's assumption of a constant defect ratio may be conservative given the overall ageing of its system.

As a result of the Tribunal's decision, the AER's draft decision to reduce TransGrid's forecast opex for defect maintenance of new growth assets was overturned. The Tribunal's ruling upheld TransGrid's revised regulatory proposal and its modelling and assumptions regarding its asset base and defect rates. The Tribunal's decision provided clarity on the reasonableness of TransGrid's opex forecast for defect maintenance of new growth assets and reinforced the importance of considering the overall ageing of the asset base when determining defect rates.