Revenue for the half to September grew by $18 million, or 4%, to $520 million, operating earnings rose 44% to $159 million and after-tax profit was up by $37 million, or 82%, to $82 million.
Trustpower chief executive Vince Hawksworth said Trustpower's diverse and flexible generation assets allowed it to take advantage of above-average prices, noting New Zealand generation benefited by strong hydrological inflows, which boosted production 20% during the period.
That meant its operating earnings rose by 24% to $127 million, he said.
During the period, generation weighted average prices were up about 12%, from $55 per MWH to $89.
``This reflects Trustpower's geographically diverse fleet of generation stations that allowed it to take advantage of record-high inflows in some parts of New Zealand while other parts were facing extremely low inflows,'' Mr Hawksworth said.
Trustpower shares were up more than 2% to $5.95 following the announcement, and up more than 21% on a year ago.
Forsyth Barr broker Damian Foster said Trustpower's $159 million operating earnings were up $40 million on a year ago and more than $19 million higher than Forsyth Barr had forecast; a ``great'' first-half result.
``There's several factors where Trustpower has done better than expected,'' Mr Foster said.
Generation costs were $9.5 million lower than forecast, higher electricity pricing boosted revenue by $4.5 million, the wages bill was $3 million lower than expected and telecommunications profit margins rose significantly, $3.2 million up on predictions.
``The strong performance relative to last year is largely due to record hydro generation volumes overlapping a period of high wholesale electricity prices ... while the retail business has also doubled its contribution by more than $15 million to $30 million,'' Mr Foster said.
Craigs Investment Partners broker Peter McIntyre said the result was driven by abnormal hydrology and was well anticipated.
He noted operating costs were down sharply as merger disruptions in the same period last year, and delayed marketing costs, impacted numbers positively.
Tilt Renewables, the solar and wind generator spun out of Trustpower last year, posted a first-half loss last week of $A2.6 million, compared with a $A110.5 million profit the year before.
Weaker wind generation on both sides of the Tasman reduced electricity production.
Mr Hawksworth said Trustpower's three remaining generation schemes in New South Wales were associated with irrigation schemes and early indications were that this summer's volumes would be ``consistent'' with earlier predictions.
Mr Hawksworth said Trustpower's ``bundling'' of essential household utilities, including power, gas, internet and phone, was ``gaining momentum''.
While customer numbers rose ``modestly'' from 385,000 to 390,000, Trustpower was on track for a 20% gain in telecommunications customers this year.
Customers with two or more bundled products rose 4% to 94,000 during the period.
Transpower kept its operating earnings guidance for the full year at $255 million to $270 million.
Mr Foster said given the strong first half, that guidance restatement looked ``a little conservative''.
He also noted it was "a little surprising'' Trustpower had kept its dividend at 17c per share, but the cautious approach comes from the uncertainty around a yet-to-be-determined charge by the Electricity Authority on Acot (avoided cost of transmission).
