Contact Energy has posted a loss for the first six months of the trading year on the back of a writedown in the value of assets.
The company, which generates about a third of the country's power, posted an after tax loss of $116 million for the six months to December because of costs associated with closing the Otahuhu power station and delaying a geothermal project.
Excluding the one off items, the company's underlying profit was $73m, which was down about four percent on a year ago.
Separately, Contact said it has agreed to sell the site of the Otahuhu station to an Auckland property development company for $30m.
Contact operates 11 power stations across New Zealand, including five geothermal stations in the central North Island, gas-fired stations in Taranaki, Waikato and Hawkes Bay, and two hydro stations in central Otago.