Company: TSLTF
Filing Date: 2025-12-12
Form Type: SUPPL
Source: 0001193125-25-317786
Chunk: 386

Company: TRANSALTA CORP
Filing Date: 2025-12-12
Form: SUPPL
Chunk 386
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 and the impact of a milder weather on the nine months ended Sept. 30, 2025. The realized merchant power price per MWh of production for the Alberta portfolio for the three and nine months ended Sept. 30, 2025 increased by $13 and $16 per MWh, respectively, compared to the same periods in 2024, primarily due to:

| • |     | Favourable hedge positions settling in the current period and production optimization, which                                   
 generated positive contributions over settled spot prices in Alberta compared to the same periods in 2024; partially offset by |

| • |     | Lower average spot power prices as explained above. |

Fuel cost per MWh for the three months ended Sept. 30, 2025 decreased by $4 per MWh, compared to the same period in 2024, due to lower natural gas prices. Fuel cost per MWh for the nine months ended Sept. 30, 2025 increased by $3 per MWh, compared to the same period in 2024, due to higher natural gas prices.

Carbon compliance cost per MWh of production for the three months ended Sept. 30, 2025 decreased by $6 per MWh, compared to the same period in 2024, primarily due to:

| • |     | Favourable impact on carbon compliance cost per MWh due to an increase of production from lower 
 carbon-emitting cogeneration facilities; partially offset by                                    |

| • |     | An increase in the carbon price per tonne from $80 in 2024 to $95 in 2025. |

Carbon compliance cost per MWh of production for the nine months ended Sept. 30, 2025 decreased by $7 per MWh, compared to the same period in 2024, primarily due to:

| • |     | Utilization of higher quantity of internally generated and externally purchased emission credits in                                                                                       
 the current period compared to the same period of prior year to settle a portion of our 2024 GHG obligation and a portion of the GHG obligation assumed in the Heartland acquisition; and |

| • |     | Favourable impact on carbon compliance cost due to an increase of production from lower 
 carbon-emitting cogeneration facilities; partially offset by                            |

| • |     | An increase in the carbon price per tonne from $80 in 2024 to $95 in 2025. |

| M40 |     | TransAlta Corporation