Mr. John Kousinioris reports

TRANSALTA PROVIDES NOTICE TO MOTHBALL SHEERNESS UNIT 1

TransAlta Corp. subsidiary Alberta Power (2000) Ltd. provided notice to the Alberta Electric System Operator on Dec. 18, 2025, that Sheerness Unit 1 will be temporarily mothballed effective April 1, 2026, for a period of up to two years. TransAlta maintains the flexibility to return the mothballed unit to service when market fundamentals or contracting opportunities are secured. The unit will remain available and fully operational through the winter season and Sheerness Unit 2 will remain fully in service.

"We have made the prudent financial decision to temporarily mothball Sheerness Unit 1 while reserving it for future economic opportunities. There is significant value at our Alberta thermal sites and we remain very pleased with the continued progress on our data centre strategy. Today's decision ensures we preserve the long-term optionality of the asset," said John Kousinioris, president and chief executive officer.

About TransAlta Corp.

TransAlta owns, operates and develops a diverse fleet of electrical power generation assets in Canada, the United States and Australia with a focus on long-term shareholder value.

We seek Safe Harbor.