Meridian Energy has lifted its profit by two-thirds.
The State owned electricity generator and retailer made $303.1 million in the year to the end of June, an increase of 64% on the previous year.
The result included a one-off gain of $154 million from the sale of the Tekapo A and B hydro stations to Genesis Energy to promote competition.
Chief executive, Tim Lusk says prices cannot stay as they are, particularly if demand lifts as the economic recovery picks up.
Mr Lusk says that although it's hard to pick when prices will climb again, competition will continue and that will be good for consumers.