The regulatory investment test for transmission (RIT-T) is a cost-benefit analysis overseen by the Australian Energy Regulator (AER). It assesses the economic and technical impact of, and preferred timing for, all major network investments in the national energy market (NEM). The RIT-T process ensures regulated transmission investment decisions are in the long term interests of customers.

RIT-T update report – 2024

The National Electricity Rules include provisions that require the RIT-T to be reapplied if there has been a material change in circumstances which, in the reasonable opinion of the RIT-T proponent, means that the preferred option identified in the RIT-T is no longer preferred.

Following the conclusion of the RIT-T for Project Marinus in June 2021, the electricity sector in Australia has continued to experience an unprecedented period of change as we transition to a net zero economy. This transition includes the accelerated closure of coal plants and a growing need for renewable generation and energy storage projects. Internationally, the emergence of an inflationary environment and concerns regarding energy security have increased the costs of delivering major transmission projects.

Given the extent of these changes, we engaged Ernst & Young (EY) in October 2023 to update its market modelling which had been initially conducted in 2020/21 for the Marinus Link’s PACR. The updated modelling used the latest data, including Australian Energy Market Operator (AEMO’s) Inputs, Assumptions and Scenarios Report, which it published in June 2023. EY completed its preliminary work in November 2023.

Following AEMO publishing its Draft 2024 ISP in December 2023, we re-engaged EY to provide a further update to its market modelling to align with inputs and results in the Draft 2024 ISP. EY’s modelling update was finalised in March 2024, which we incorporated in our updated cost-benefit assessment.

The reports below and associated models detail results from our RIT-T update and EY’s associated market modelling. Marinus Link welcomed feedback from communities and stakeholders in early 2024.

Project Marinus – Project Assessment Conclusions Report
(July 2018 – June 2021)

The publication of this report marks the culmination of the Project Marinus RIT-T process, which began in 2018 with the publication of the Project Specification Consultation Report (PSCR). The report outlines our stakeholder engagement activities, economic and technical analysis and results in the identification of a preferred option that maximises the net economic benefits to the NEM.

Project Marinus PACR (summary)
Project Marinus RIT-T Project Assessment Conclusions Report (PACR)

Ernst & Young market modelling attachment
GHD FCAS modelling attachment
Jacobs project cost estimate

Supplementary Analysis Report
(November – December 2020)

The Report responds to stakeholder feedback received on the Project Assessment Draft Report (PADR) analysis and takes into consideration the updated scenarios, inputs and assumptions of the 2020 Integrated System Plan (ISP) released by the Australian Energy Market Operator (AEMO).

On Wednesday, 25 November 2020, 11am to 12:30pm (AEDT), we held a webinar to discuss this report.

View the

Submissions to Supplementary Analysis Report

Following the submission period to 7 December 2020, the following submissions were received:

Project Assessment Draft Report (PADR)
(December 2019 – April 2020)

TasNetworks published the Project Marinus Project Assessment Draft Report (PADR) in early 2020. The PADR takes into account feedback from submissions received during the consultation period following the PSCR’s release.

TasNetworks will be receiving feedback on the PADR over the coming months as part of the RIT-T consultation process, including briefings in Melbourne, Sydney and Hobart in early 2020.

Subsequent to publishing the PADR, additional data files are available which contain detailed information relating to PADR modelling assumptions and results. You can view the PADR files (ZIP file 12MB).

Hourly results of the PADR simulation results are available upon request. Please contact us and we will share a link to download the files (up to 1Gb per .zip). Please state “hourly results request” in the subject. Further explanation of how TasNetworks has used public data in the PADR can be provided on request where reasonably practicable to do so, and where requested for the purpose of understanding PADR modelling in order to participate in the RIT-T consultation process.

A copy of the slides presented at the most recent PADR forum can be found here: PADR forum slides.

In response to stakeholder feedback, TasNetworks publishes this explanatory note regarding computation of benefits and costs for Marinus Link. You can also take a look at the accompanying explainer spreadsheet.

Stakeholder Submissions PADR

TasNetworks has received feedback on the PADR as part of the RIT-T consultation process.

A total of 15 submissions were received, of which two were confidential.
Non-confidential stakeholder submissions are provided below. Responses to this consultation will be summarised in the next stage of Marinus Link investigation.

Project Specification Consultation Report
(July 2019 – September 2019)

Marinus Link published its initial Project Specification Consultation Report (PSCR) as part of the RIT-T process in July 2018. This report and the feedback it has received is available below.

Stakeholder Submissions PSCR

Business Case Assessment (2019)

TasNetworks published its Business Case Assessment Report (BCA) for Marinus Link and supporting North West transmission developments.

The analysis showed that Marinus Link and the supporting transmission developments will support Australia’s transition to a low emissions future by delivering the low cost, reliable, and clean energy that customers expect. The investment will provide additional dispatchable capacity to a transforming National Electricity Market (NEM).

Assessment for the feasibility and business case for Marinus Link and supporting transmission developments) commenced in 2017 with $20 million in funding from the Tasmanian Government through TasNetworks and the Australian Government through the Australian Renewable Energy Agency (ARENA). The feasibility and business case assessment phase of the project concluded with the release of the Business Case Assessment Report in December 2019.

The Business Case Assessment and supporting documents including a summary document and fact sheet can be downloaded as a PDF by clicking on the links below.