Company: TSLTF
Filing Date: 2025-12-12
Form Type: SUPPL
Source: 0001193125-25-317786
Chunk: 374

Company: TRANSALTA CORP
Filing Date: 2025-12-12
Form: SUPPL
Chunk 374
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 million and $310 million for the three and nine months ended Sept. 30, 2025, respectively (Sept. 30, 2024 — $105 million and $316 million), to adjusted gross margin — gross margin of $90 million and                     
 $294 million for the three and nine months ended Sept. 30, 2025, respectively (Sept. 30, 2024 — $101 million and $303 million), to Adjusted EBITDA and Adjusted earnings before income taxes — earnings before income taxes of 
 $67 million and $226 million for the three and nine months ended Sept. 30, 2025, respectively (Sept. 30, 2024 — $80 million and $239 million).                                                                                 |

Adjusted revenues for the three months ended Sept. 30, 2025 decreased compared to the same period in 2024, primarily due to:

| • |     | Lower ancillary services revenue due to lower availability and production optimization between the 
 Gas and Hydro segments;                                                                            |

| • |     | Lower environmental and tax attributes revenue due to lower sales of emission credits to third 
 parties; and                                                                                   |

| • |     | Lower spot power prices in the Alberta market; partially offset by |

| • |     | Higher merchant and contract volumes; and |

| • |     | Higher regulated transmission revenues related to the reimbursement of costs incurred in prior 
 periods.                                                                                       |

Adjusted EBITDA and Adjusted earnings before income taxes for the three months ended Sept. 30, 2025 decreased compared to the same period in 2024, primarily due to lower adjusted revenues as explained by the factors above. Earnings before income taxes for the three months ended Sept. 30, 2025 decreased compared to the same period in 2024 due to:

| • |     | Lower adjusted earnings before income taxes; partially offset by |

| • |     | Higher unrealized                                               
 mark-to-market gains due to favourable forward pricing changes. |

Adjusted revenues for the nine months ended Sept. 30, 2025 decreased compared to the same period in 2024, primarily due to:

| • |     | Lower ancillary services revenue due to lower availability and production optimization between the 
 Gas and Hydro segments; and                                                                        |

| • |     | Lower spot power prices in Alberta; partially offset by |

| • |     | Higher merchant and contract volumes; |

| • |     | Higher regulated transmission revenues related to the reimbursement of costs