Genesis Energy has more than doubled its annual net profit to $104.8 million, despite losing customers.
The country's largest electricity retailer said the result was achieved against a backdrop of variable weather, ongoing intense retail competition, a subdued wholesale market and falling oil prices.
The number of customers fell 1.7 percent to nearly 636,676, but the volume of retail gas and LPG sales grew.
Genesis chief executive Albert Brantley said customer numbers have stablised over the past few months.
Mr Brantley said he was confident the company could match or better last year's operating profit, which rose 12 percent to $344.8 million.
He said Genesis would go ahead with the planned closure of its two remaining Rankine units at Huntly, despite Contact Energy's decision to close its Otahuhu plant in Auckland at the end of September.
Mr Brantley also announced he would retire next June.
He said his replacement would not necessarily have an engineering background, as the job now required a different mix of skills than what he himself possessed.