Trustpower says power customers will get no respite from rising prices, as demand grows and the cost of building new generation increases.
The company's profit jumped 14% to just over $119 million in the year to March, as cost cutting offset lower wholesale prices.
Chief executive Vince Hawksworth says the electricity market will be increasingly volatile, which will result in higher prices in the future.
He says the Government's plan to swap assets among state owned power companies has created some uncertainty in the market and may actually led to higher prices in some instances.
Meanwhile, the board of Trustpower has given the go ahead for a new wind farm next to the Waipori hydro scheme, which is due to be completed in May next year at a cost of $75 million.
Mr Hawksworth says the company is keen to invest in more renewable projects, but only if they return value to shareholders.