Underlying full year earnings at Mighty River Power are down by a third to $139.6 million.
The state-owned power company made an after-tax profit of $85 million, down by nearly half from the record $159.6 million the previous year.
The fall is due to the Waikato drought severely affecting water levels and hydro production during the year.
Revenues were flat at $1.1 billion for the year to June.
The company attracted 30,000 more customers over the year to 412,000 and now has 21% of the market. But it had to pay an extra $9 million in sales and marketing costs in order to achieve that.
Chief executive Doug Heffernan says it has been a challenging year.
The company will pay the Government a final dividend of $30.3 million.