Power company Mercury's half year net profit has fallen 20 percent to $104 million as it generated less hydro power and had to pay more to cover future demand.
However, its underlying earnings were steady at $114m as it charged higher prices for power when supply was low late last year, and its revenue rose 13 percent to $1 billion.
Chair Joan Withers said the financial result was pleasing given the difficult trading conditions.
"Mercury came close to matching last financial year's record first half performance despite less favourable hydro conditions in the Waikato catchment, leading to lower hydro generation."
"Earnings reflected strong execution across the entire business, underpinned by record spot market prices, a lift in net sales yields, a disciplined focus on costs and strong execution of the planned work programme," Ms Withers said.
Mercury lost 7000 customers in the period.
Low water levels at its hydro-plants on the Waikato River and an outage at the country's largest gas storage facility, saw electricity spot prices hit a seven-year high in October.
Chief executive Fraser Whineray said Mercury had learned from the challenge.
"There were still lessons, and opportunities for improvement in how the sector responds.
"We believe the electricity market would benefit from a much stronger disclosure regime from thermal generators," Mr Whineray said.
Mercury confirmed its full year underlying earnings were on track to be $515m, as well as an increased dividend.