Customer numbers dropped by 50,000 to 224,000 during the year, after TrustPower pulled out of the Auckland, Wellington and Christchurch residential retail markets to give a better generation-retail balance, thus reducing its exposure to the volatility of the wholesale electricity market. As a consequence revenue dipped by 5% but expenses fell by 8%.

The valuation of TrustPower's generation assets - 34 hydro stations and this country’s biggest windfarm, on the Tararua Ranges near Palmerston North - increased by NZ$421 million as a result of an independent, three-yearly review.

Stage two of its Tararua windfarm is to be opened by Energy Minister Pete Hodgson tomorrow.

"The increase in asset values reflects the higher earning potential of TrustPower's renewable generation portfolio in a market which will be affected by the higher prices for new contracted gas post the rundown of Maui," said company chairman Harold Titter.

Trustpower has three main shareholders - infrastructure investor Infratil (35.2% holding), Tauranga Energy Consumer Trust (28.6%) and US energy company Alliant (23.8%).

The past year saw company shareholder funds increase from NZ$604 million to NZ$866 million, even after a NZ$151 million capital return last June.

Meanwhile, Horizon Energy Distribution - one of only two lines companies listed on the NZ Stock Exchange - has posted a NZ$6.3 million net profit.

The Whakatane-based company’s profit was up over 13%, from slightly lower trading revenues but increased non-trading revenues earned from the sale of surplus property and a subdivision development.