TransAlta Provides Notice to Mothball Sheerness Unit 1
Rhea-AI Summary
TransAlta (NYSE: TAC) announced that Alberta Power (2000) Ltd., a subsidiary, provided notice on Dec 18, 2025 that Sheerness Unit 1 will be temporarily mothballed effective Apr 1, 2026 for a period of up to two years. The company said the unit will remain available and fully operational through the winter season and that Sheerness Unit 2 will remain fully in service. TransAlta retains the flexibility to return Unit 1 to service if market fundamentals or contracting opportunities emerge, and described the action as preserving the long-term optionality of the asset while supporting its data centre strategy.
Positive
- Mothball effective Apr 1, 2026 for up to 2 years
- Unit 1 remains available and fully operational through winter
- Unit 2 stays in service, maintaining on-site capacity
- Flexibility to restart when market fundamentals or contracts arise
Negative
- Unit 1 removed from normal operation starting Apr 1, 2026
- Thermal active units reduced to one on site while mothballed
News Market Reaction
On the day this news was published, TAC declined 0.32%, reflecting a mild negative market reaction.
Data tracked by StockTitan Argus on the day of publication.
Key Figures
Market Reality Check
Peers on Argus
While TAC is down 5.67%, most close peers like KEN, PAM, NRG and VST show small gains (up between 0.23% and 1.36%), with only TLN slightly negative at -0.85%. This points to a stock-specific reaction rather than a sector-wide move.
Historical Context
| Date | Event | Sentiment | Move | Catalyst |
|---|---|---|---|---|
| Dec 17 | Regulatory operations order | Neutral | -5.7% | DOE ordered Centralia Unit 2 remain available for 90 days. |
| Dec 12 | Dividend declaration | Positive | -1.2% | Declared common and preferred share dividends for early 2026. |
| Dec 09 | Long-term tolling deal | Positive | +3.5% | Signed 16-year 700 MW tolling agreement enabling coal-to-gas conversion. |
| Nov 17 | Asset acquisition | Positive | -2.3% | Agreed to buy 310 MW Ontario gas portfolio expected to be accretive. |
| Nov 17 | Counterparty asset sale | Positive | -2.3% | Hut 8 announced sale of 310 MW portfolio to TransAlta. |
Recent history shows multiple strategic or capital-positive announcements followed by negative price reactions, suggesting the stock often trades lower around constructive corporate updates, with only the Centralia conversion agreement aligning positively with its news tone.
Over the past months, TransAlta has announced several significant developments. On Nov 17, it agreed to acquire a 310 MW Ontario gas portfolio for $95 million, expected to be accretive, yet shares fell 2.33%. The same day, a Hut 8 release on the same assets coincided with the same decline. A Dec 9 long-term 700 MW Centralia tolling and coal-to-gas conversion deal saw shares rise 3.54%. However, subsequent dividend declarations on Dec 12 and a DOE order on Dec 17 were followed by negative moves. Today’s mothballing notice continues the theme of active portfolio repositioning.
Market Pulse Summary
This announcement details a temporary mothballing of Sheerness Unit 1 effective April 1, 2026 for up to two years, while keeping Sheerness Unit 2 fully operational. Management emphasizes preserving asset optionality and links the move to broader value at Alberta thermal sites and its data centre strategy. In context of recent acquisitions and long-term conversion projects, investors may watch how contracting progress, regulatory developments, and future decisions on returning the unit to service shape overall generation mix and cash flow visibility.
AI-generated analysis. Not financial advice.
CALGARY, Alberta, Dec. 18, 2025 (GLOBE NEWSWIRE) -- Alberta Power (2000) Ltd., a subsidiary of TransAlta Corporation (TransAlta or the Company) (TSX: TA) (NYSE: TAC), provided notice to the Alberta Electric System Operator on December 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 Corporation:
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. TransAlta provides municipalities, medium and large industries, businesses and utility customers with affordable, energy efficient and reliable power. Today, TransAlta is one of Canada’s largest producers of wind power and Alberta’s largest producer of thermal generation and hydro-electric power. For over 114 years, TransAlta has been a responsible operator and a proud member of the communities where we operate and where our employees work and live. TransAlta aligns its corporate goals with the UN Sustainable Development Goals and the Future-Fit Business Benchmark, which also defines sustainable goals for businesses. Our reporting on climate change management has been guided by the International Financial Reporting Standards (IFRS) S2 Climate-related Disclosures Standard and the Task Force on Climate-related Financial Disclosures (TCFD) recommendations. TransAlta has achieved a 70 per cent reduction in GHG emissions or 22.7 million tonnes CO2e since 2015 and received an upgraded MSCI ESG rating of AA.
For more information about TransAlta, visit our web site at transalta.com.
Cautionary Statement Regarding Forward-Looking Information
This news release includes “forward-looking information,” within the meaning of applicable Canadian securities laws, and “forward-looking statements,” within the meaning of applicable United States securities laws, including the Private Securities Litigation Reform Act of 1995 (collectively referred to herein as “forward-looking statements”). Forward-looking statements are not facts, but only predictions and generally can be identified by the use of statements that include phrases such as “may”, “will”, “believe”, “expect”, “estimate”, “anticipate”, “intend”, “plan”, “forecast”, “continue” or other similar words. Forward-looking statements are intended to provide the reader information about management’s current expectations and plans and readers are cautioned that such information may not be appropriate for other purposes. Forward-looking statements are subject to important risks and uncertainties and are based on certain key assumptions. All forward-looking statements reflect TransAlta’s beliefs and assumptions based on information available at the time the statements were made and as such are not guarantees of future performance. As actual results could vary significantly from the forward-looking statements, you should not put undue reliance on forward-looking statements and should not use future-oriented information or financial outlooks for anything other than their intended purpose. We do not update our forward-looking statements due to new information or future events, unless we are required to by law. For additional information on the assumptions made, and the risks and uncertainties which could cause actual results to differ from the anticipated results, refer to our most recent MD&A and the 2024 Integrated Report, including the section titled “Governance and Risk Management” in our MD&A for the year ended December 31, 2024, filed under TransAlta’s profile on SEDAR+ at www.sedarplus.ca and with the U.S. Securities and Exchange Commission at www.sec.gov.
Note: All financial figures are in Canadian dollars unless otherwise indicated.
For more information:
| Investor Inquiries: | Media Inquiries: |
| Phone: 1-800-387-3598 in Canada and US | Phone: 1-855-255-9184 |
| Email: investor_relations@transalta.com | Email: ta_media_relations@transalta.com |
FAQ
What did TransAlta (TAC) announce about Sheerness Unit 1 on Dec 18, 2025?
Will Sheerness Unit 1 operate through the winter before mothballing for TAC?
Does TransAlta (TAC) plan to keep Sheerness Unit 2 in service?
Can TransAlta restart Sheerness Unit 1 before the two-year mothball period ends?
How long is the mothball period for Sheerness Unit 1 under TransAlta's notice?
