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Portfolio Assessment

A market power mitigation framework commenced with the new Wholesale Electricity Market (WEM) on 1 October 2023. Under that framework the Economic Regulation Authority (ERA) must conduct a portfolio assessments and market power tests at regular, specified timeframes throughout the year. The first of the two forms of assessment assigns facilities to portfolios based on registration, ownership, or operational control. The second form, constrained portfolio assessment, is based on those facilities subject to a binding network constraint during a Rolling Test Window. Following identification of portfolios and constrained portfolios a materiality threshold is then applied (the market power test).

Allocation to a material portfolio or material constrained portfolio places governance obligations on facilities within material portfolios to maintain records. The process also places obligation on the ERA to monitor offers into the real time market from material portfolios. The ERA’s monitoring and surveillance activities are not confined to material portfolios.

The ERA is guided by the WEM Procedure: Portfolio Determination when completing this work.


The ERA must complete its first assessment to identify each portfolio by 1 December 2023 (WEM Rule 1.62.1(a)), then twice each year by 1 April and 1 October (WEM Rule 2.16B.1(a)). After identifying portfolios, it must apply a market power test to determine material portfolios (WEM Rule 2.16C.1).

Constrained Portfolios

The ERA must also complete its initial assessment to identify each constrained portfolio 10 business days after the end of the first rolling test window (RTW), that commenced on 1 October 2023 (WEM Rule 1.62.1(b)). After the initial assessment constrained portfolios will be assessed the end of each RTW (WEM Rule 2.16B.2), with a market power test applied after to determine Material Constrained Portfolios (WEM Rule 2.16C.2). 

Portfolios and Material Portfolios

Date  Documents File type
05-Dec-23 Determination Adobe PDF 310 kB
Page last updated: 05 Dec 2023