Appendix to the TasNetworks Supplementary Analysis Report Addendum to Project Marinus PADR economic modelling report Tasmanian Networks Pty Ltd 9 November 2020 Ernst & Young Tel: +61 7 3011 3333 111 Eagle Street Fax: +61 7 3011 3100 Brisbane QLD 4000 Australia ey.com/au GPO Box 7878 Brisbane QLD 4001 Notice Ernst & Young (“we” or “EY”) was engaged on the instructions of Tasmanian Networks Pty Ltd (“TasNetworks” or “Client”) to provide market modelling in relation to the proposed Marinus Link interconnector (“Project”), in accordance with the contract dated 14 June 2018. The results of EY’s work, including the assumptions and qualifications made in preparing the report, are set out in EY’s report dated 27 November 2019 ("Report") and this report dated 9 November 2020 (“Addendum”) which is an addendum to the Report and has been prepared at the specific request of the Client to update the scenarios and various input assumptions to align with more recent data. This Addendum must be read in conjunction with the Report1 to understand the full context and details of the model used to compute the long-term least-cost generation development plan and gross market benefits of Marinus Link. The Report and Addendum should be read in their entirety including this notice, the applicable scope of the work and any limitations. A reference to the Report includes any part of the Report and Addendum. No further work has been undertaken by EY since the date of the Report or the Addendum to update them. Except as described in this Addendum, no further work has been undertaken by EY since the date of the Report to update its contents. EY has prepared the Report and Addendum under the directions of the Client and as per the guidance included in the RIT-T and followed the process outlined therein. EY has not been engaged to act, and has not acted, as advisor to any other party. Accordingly, EY makes no representations as to the appropriateness, accuracy or completeness of the Report and Addendum for any other party's purposes. No reliance may be placed upon the Report and Addendum or any of its contents by any party other than the Client (“Third Parties”). Any Third Party receiving a copy of the Report and Addendum must make and rely on their own enquiries in relation to the issues to which the Report and Addendum relates, the contents of the Report and Addendum and all matters arising from or relating to or in any way connected with the Report and Addendum or their contents. EY disclaims all responsibility to any Third Parties for any loss or liability that the Third Parties may suffer or incur arising from or relating to or in any way connected with the contents of the Report, the provision of the Report and Addendum to the Third Parties or the reliance upon the Report and Addendum by the Third Parties. No claim or demand or any actions or proceedings may be brought against EY arising from or connected with the contents of the Report or Addendum or the provision of the Report and Addendum to the Third Parties. EY will be released and forever discharged from any such claims, demands, actions or proceedings. Our work commenced on 6 January 2020 and was completed on 21 October 2020. Therefore, our Report and Addendum does not take account of events or circumstances arising after 21 October 2020 and we have no responsibility to update the Report or Addendum for such events or circumstances. 1 27 November 2019, Project Marinus PADR economic modelling report. Available at: https://www.marinuslink.com.au/wp- content/uploads/2019/12/attachment-1-ernst-and-young-marketing-modelling-report.pdf. Accessed 24 September 2020. A member firm of Ernst & Young Global Limited EY i Liability limited by a scheme approved under Professional Standards Legislation Ernst & Young Tel: +61 7 3011 3333 111 Eagle Street Fax: +61 7 3011 3100 Brisbane QLD 4000 Australia ey.com/au GPO Box 7878 Brisbane QLD 4001 In preparing the Report and this Addendum we have considered and relied upon information from a range of sources believed to be reliable and accurate. We do not imply, and it should not be construed, that we have verified any of the information provided to us, or that our enquiries could have identified any matter that a more extensive examination might disclose. The work performed as part of our scope considers information provided to us and a number of combinations of input assumptions relating to future conditions, which may not necessarily represent actual or most likely future conditions. Additionally, modelling work performed as part of our scope inherently requires assumptions about future behaviours and market interactions, which may result in forecasts that deviate from future conditions. There will usually be differences between estimated and actual results, because events and circumstances frequently do not occur as expected, and those differences may be material. We take no responsibility that the projected outcomes will be achieved, if any. We highlight that our analysis, Report and Addendum do not constitute investment advice or a recommendation to you on a future course of action. We provide no assurance that the scenarios we have modelled will be accepted by any relevant authority or third party. Our conclusions are based, in part, on the assumptions stated and on information provided by the Client and other information sources used during the course of the engagement. The modelled outcomes are contingent on the collection of assumptions as agreed with the Client and no consideration of other market events, announcements or other changing circumstances are reflected in the Report or this Addendum. Neither EY nor any member or employee thereof undertakes responsibility in any way whatsoever to any person in respect of errors in this Report arising from incorrect information provided by the Client or other information sources used. EY has consented to the Addendum being published electronically on the Client’s website alongside the Report for informational purposes only. EY has not consented to distribution or disclosure beyond this. The material contained in the Report and Addendum, including the EY logo, is copyright. The copyright in the material contained in the Report and Addendum itself, excluding EY logo, vests in the Client. The Report and Addendum, including the EY logo, cannot be altered without prior written permission from EY. EY’s liability is limited by a scheme approved under Professional Standards Legislation. A member firm of Ernst & Young Global Limited EY ii Liability limited by a scheme approved under Professional Standards Legislation Table of contents 1. Executive summary........................................................................................................ 1 2. Introduction .................................................................................................................. 5 2.1 Conventions used in this document ........................................................................... 6 3. Methodology and input assumptions ................................................................................ 7 3.1 Long-term investment planning model overview ......................................................... 7 3.2 Cost-benefit analysis ................................................................................................ 8 3.3 Model improvements and data updates since the Project Assessment Draft Report ........ 8 4. Scenarios and sensitivity assumptions ........................................................................... 15 4.1 Scenarios .............................................................................................................. 15 4.2 Differences in modelling and assumption relative to AEMO’s 2020 Integrated System Plan 18 4.3 Sensitivities ........................................................................................................... 22 5. Transmission and demand ............................................................................................ 23 5.1 Size and timing of other interconnector developments .............................................. 23 5.2 Interconnector loss assumptions ............................................................................. 24 5.3 Demand ................................................................................................................ 25 6. Supply ........................................................................................................................ 26 6.1 Inertia constraint ................................................................................................... 26 6.2 Reserve constraint ................................................................................................. 27 6.3 Complex heat rates ................................................................................................ 28 6.4 Tasmanian Renewable Energy Target ...................................................................... 28 7. Marinus Link forecast gross market benefits .................................................................. 30 7.1 Summary of forecast gross market benefits ............................................................. 30 7.2 Sensitivities ........................................................................................................... 31 Appendix A List of abbreviations ......................................................................................... 33 A member firm of Ernst & Young Global Limited EY iii Liability