A warm winter, low hydro-lake levels, and a power station outage have dented Tauranga-based Trustpower's half-year profit.
Trustpower's net profit for the six months ended September was $39 million compared with the previous year's $65m, with expenses growing at twice the rate of revenue.
Trustpower generates and sells electricity, and also offers gas, mobile phone and broadband services. Its number of customers grew marginally to 406,000 but there was stronger growth in consumers taking two or more services, and it has 100,000 telecommunication customers.
Trustpower's generation was affected by a three-month outage at its Highbank hydro station in the South Island.
Chief executive Vince Hawksworth said it was a mixed result in a difficult period.
"The key issue is that our generation volumes were down 15 percent and that was largely because it didn't rain in the right places at the right time."
He said one of the positives was the further growth in the bundling of its telecommunications with energy services, which grew nearly 9 percent. The company had invested in its broadband network to ensure sufficient capacity for the recent Rugby World Cup.
Mr Hawksworth said the second half should be better, but it would have to cope with the seasonal slowdown in demand during the summer period. The company has marginally lowered its earnings forecast range for the full year to between $200m-$215m.
He said Trustpower had no plans to build new generation but would look to improve the production of its existing stations as well as look for the best links with other generators to make up its power needs at the best prices.