The country's third largest electricity state owned enterprise (SOE) is defending prices charged to power users.
Prices have risen by more than twice the rate of inflation in the past decade.
In the last financial year, Mighty River Power's profits soared. Its regular and special dividends to the state were $229.8 million.
The company's chief executive, Doug Heffernan, was asked at a select committee in Parliament on Wednesday whether that suggests electricity prices are too high.
He replied that prices have been set at a level to pay for future energy developments.
"There's a lot more effort than would have gone on back in the 1990s around preparing sites, getting consents - so your speed to actually build and get to market is as short as possible," Mr Heffernan said.
"The sector is in a much more responsive position to build capacity than any time in the last 15 years."