Company: TSLTF
Filing Date: 2025-12-12
Form Type: SUPPL
Source: 0001193125-25-317786
Chunk: 388

Company: TRANSALTA CORP
Filing Date: 2025-12-12
Form: SUPPL
Chunk 388
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 initiatives in the first and second quarters of 
 2025 and in the third and fourth quarters of 2024, compared to same periods in the prior year;  |

| • |     | Return to service of the Kent Hills wind facilities and the impact from the Horizon Hill and White 
 Rock wind facilities which achieved commercial operation in the first half of 2024;                |

| • |     | The addition of the Heartland facilities and associated corporate costs in all three quarters of 
 2025 and part of the fourth quarter of 2024;                                                     |

| • |     | Higher costs stemming from the planning, design and implementation of an upgrade to our ERP system 
 in all three quarters of 2025 and the fourth quarter of 2024; and                                  |

| • |     | In the fourth quarter of 2024, penalties assessed by the Alberta Market Surveillance Administrator     
 for self-reported contraventions pertaining to Hydro ancillary services provided during 2021 and 2022. |

Depreciation has been impacted by:

| • |     | Revisions in the useful lives of certain facilities that occurred in the third quarter 2024; |

| • |     | An increase in depreciation due to the impact from the White Rock and Horizon wind facilities which 
 achieved commercial operation in the first half of 2024; and                                        |

| • |     | The acquisition of Heartland in the fourth quarter of 2024. |

Higher asset impairment charges due to:

| • |     | An impairment charge on the Required Divestitures classified as held for sale in the first quarter 
 of 2025;                                                                                           |

| • |     | Development projects that are no longer proceeding in the first and second quarters of 2025 and the 
 third and fourth quarters of 2024;                                                                  |

| • |     | Increase in decommissioning provisions for retired assets due to changes in estimated cash flows in 
 the third quarter of 2023 and 2024;                                                                 |

| • |     | Increase in decommissioning provisions for retired assets due to lower discount rates in the second 
 and third quarter of 2025;                                                                          |

| • |     | Changes in the expected timing of when decommissioning occurs, impacting the calculation of 
 decommissioning provision in the third and fourth quarters of 2024;                         |

| • |     | Impairment reversal related to certain Energy Transition assets reclassified to Assets held for 
 sale in the first quarter of 2025; and