Genesis Energy has more than doubled its annual profit on the back of high wholesale power prices and a jump in the value of its Huntly Power Station units.
The country's biggest power retailer made a net profit of $59 million in the year ended June compared with $20m last year, which included large writedowns in the value of its generation assets.
The profit was lifted by a $35m gain in the value of its Huntly gas and coal fired Rankine units, which were used through the year to back up power supplies hit low hydro lakes and gas shortages.
Genesis chief executive Marc England said it built momentum in its retail business while market conditions were challenging.
"Genesis' flexible generation assets have ensured energy security for all New Zealanders during a period of unplanned and significant natural gas supply constraints and low hydro inflows."
Revenue rose 17 percent to $2.7 billion but its underlying earnings were little changed, up 0.8 percent to $363m.
However, income from oil and gas from the Kupe field, which Genesis owns 40 percent of, was lower.
It also branched out with a 40 percent stake in the car share company Yoogo for $2m to help its customers reduce their carbon emissions.
"[Yoogo] will provide significant opportunity for Genesis' business customers, many of whom are on the verge of transitioning pool car fleets to electric vehicles," Mr England said.
"[It] will reduce average running cost per kilometre, avoid unneeded capital expenditure, lower carbon emissions and enable more flexible transportation for New Zealand businesses and their employees."
Genesis' costs rose as it spent more on technology projects and generation maintenance.
The speed at which it lost customers, called the churn rate, fell in the year.