The settlement of the sale and purchase agreement will take place on 1 June 2011.
The combined 185 MW hydro power stations are located on the Lake Tekapo in South Island.
The company has also signed a four year water management agreement with the vendor, Meridian Energy, which requires it to sell a portion of the output from the Tekapo stations to Meridian.
The acquisition will provide the company with a more balanced and diversified generation portfolio.
