The company attributes the rise to gaining more customers, selling more power and making a big capital gain on its July purchase of Australian hydro and wind assets.
The electricity generator and retailer says its net profit of $89.2 million for the six months ended September was struck on a rise in sales of more than 20 percent, to $505 million.
Trustpower says the Green State Power hydro and wind stations in New South Wales which it bought in July are now worth $25 million more than the $81.3 million it paid.