Company: TSLTF
Filing Date: 2025-12-12
Form Type: SUPPL
Source: 0001193125-25-317786
Chunk: 367

Company: TRANSALTA CORP
Filing Date: 2025-12-12
Form: SUPPL
Chunk 367
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.3 |     |      | 93.7 |     |                         | 94.3 |     |      | 93.8 |
| Gas               |     |                         | 95.4 |     |      | 96.3 |     |                         | 93.7 |     |      | 95.4 |
| Energy Transition |     |                         | 83.3 |     |      | 90.0 |     |                         | 87.2 |     |      | 76.1 |
| Availability (%)  |     |                         | 92.7 |     |      | 94.5 |     |                         | 93.1 |     |      | 92.5 |

Availability is an important measure for the Company as it represents the percentage of time a facility is available to produce electricity, and is an indicator of the overall performance of the fleet. Availability is impacted by planned and unplanned outages, and derates. The Company schedules dedicated time (planned outages) to maintain, repair or make improvements to the facilities at a time that will minimize the impact to operations. In high price environments, actual outage schedules may shift or change to accelerate the return to service of the unit. Availability for the three months ended Sept. 30, 2025, was 92.7 per cent compared to 94.5 per cent in the same period in 2024. Lower availability compared to the prior period was primarily due to:

| • |     | Higher planned maintenance outages in the Hydro segment; |

| • |     | Higher unplanned outages at the Centralia facility in the Energy Transition segment; and |

| • |     | Higher derates in the Gas segment. |

Availability for the nine months ended Sept. 30, 2025 was 93.1 per cent compared to 92.5 per cent in the same period in 2024. Higher availability compared to the same period in 2024 was primarily due to:

| • |     | Lower planned and unplanned outages at the Centralia facility in the Energy Transition segment; and |

| • |     | The impact from the White Rock and Horizon Hill wind facilities which achieved commercial operation          
 in the first half of 2024 and operated at higher availability during the current period; partially offset by |

| • |     | Higher planned and unplanned outages in the Gas segment; and |

| • |     | Higher planned maintenance outages in the