Company: TSLTF
Filing Date: 2025-12-12
Form Type: SUPPL
Source: 0001193125-25-317786
Chunk: 345

Company: TRANSALTA CORP
Filing Date: 2025-12-12
Form: SUPPL
Chunk 345
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 |     | Illiquid future power  
 prices (per MWh)       
 Illiquid future REC(2) 
 prices (per unit)      
 Wind discounts         |     | Price decrease or increase of US$6          
 Price decrease of US$12 or increase of US$8 
 0% decrease or 6% increase                  |     | +42 / -30        |
| Long-term wind energy sale — Canada       |     | Long-term price forecast |     | Illiquid future power  
 prices (per MWh)       
 Wind discounts         |     | Price decrease of $57 or increase of $10    
 15% decrease or 5% increase                 |     | +53 / -17        |
| Long-term wind energy sale — Central U.S. |     | Long-term price forecast |     | Illiquid future power  
 prices (per MWh)       
 Wind discounts         |     | Price decrease of US$4 or increase of US$3  
 2% decrease or 2% increase                  |     | +84 / -77        |

| (1) | Potential change in fair value represents the total increase or decrease in recognized fair value 
 that would arise from the use of the reasonably possible changes of all unobservable inputs.      |

| (2) | Renewable energy credits. |

| TransAlta Corporation |     | F19 |

a. Long-Term Wind Energy Sale – Eastern U.S. The Company is party to a long-term contract for differences (CFD) for the offtake of 100 per cent of the generation from its 90 MW Big Level wind facility. The CFD, together with the sale of electricity generated into the PJM Interconnection at the prevailing real-time energy market price, achieve the fixed contract price per MWh on proxy generation. Under the CFD, if the market price is lower than the fixed contract price, the customer pays the Company the difference and if the market price is higher than the fixed contract price, the Company refunds the difference to the customer. The customer is also entitled to the physical delivery of environmental attributes. The contract expires in December 2034. The contract is accounted for as a derivative with changes in fair value presented in revenue. b. Long-Term Wind Energy Sale – Canada In Alberta, the Company is party to two Virtual Power Purchase Agreements (VPPAs) for the offtake of 100 per cent of the generation from its 130 MW Garden Plain wind facility. The VPPAs, together with the