TransAlta Corporation: News Release

CALGARY, ALBERTA--(Marketwire - Sept. 4, 2012) - TransAlta Corporation (TransAlta) (TSX:TA) (NYSE:TAC) announced today that it is commencing an offering of 19,250,000 of its Common Shares.

The expected offering price of Cdn $14.30 per Common Share will result in gross proceeds to TransAlta of approximately Cdn $275 million. TransAlta has granted the underwriters an over-allotment option to purchase up to an additional 2,887,500 of its Common Shares at the same price, exercisable in whole or in part at any time for 30 days following closing of the offering. Gross proceeds to TransAlta if the over-allotment option is exercised in full are expected to be approximately Cdn $317 million.

Proceeds from the offering will be used to fund future growth capital expenditures, including to partially fund the acquisition of the Solomon power station, to repay short term debt, and for general corporate purposes. The completion of the offering is not contingent on the closing of the acquisition of the Solomon power station. If the acquisition does not close, proceeds from the offering will be used to fund future growth capital expenditures, to repay short term debt, and for general corporate purposes.

This news release does not constitute an offer to sell or a solicitation of an offer to buy the Common Shares in any jurisdiction. The Common Shares offered have not been and will not be registered under the United States Securities Act of 1933, as amended, and may not be offered or sold within the United States absent registration under the U.S. Securities Act or an applicable exemption from such registration requirements. The Common Shares are being offered within the United States only to qualified institutional buyers and outside the United States in compliance with Regulation S under the Securities Act.

TransAlta is a power generation and wholesale marketing company focused on creating long-term shareholder value. TransAlta maintains a low-to-moderate risk profile by operating a highly contracted portfolio of assets in Canada, the United States and Australia. TransAlta's focus is to efficiently operate our geothermal, wind, hydro, natural gas and coal facilities in order to provide our customers with a reliable, low-cost source of power. For 100 years, TransAlta has been a responsible operator and a proud contributor to the communities where we work and live. TransAlta is recognized for its leadership on sustainability by the Dow Jones Sustainability North America Index, the FTSE4Good Index and the Jantzi Social Index. TransAlta is Canada's largest investor-owned renewable energy provider.

This news release may contain forward looking statements, including statements regarding the business and anticipated financial performance of TransAlta Corporation. These statements are based on TransAlta Corporation's belief and assumptions based on information available at the time the assumption was made. These statements are subject to a number of risks and uncertainties that may cause actual results to differ materially from those contemplated by the forward-looking statements. Some of the factors that could cause such differences include, pricing in the market place, our inability to enter into long term contracts due to prevailing market conditions, legislative or regulatory developments, competition, global capital markets activity, changes in interest rates, currency exchange rates, inflation levels and general economic conditions in geographic areas where TransAlta Corporation operates.

Note: All financial figures are in Canadian dollars unless noted otherwise.