Mighty River Power has officially taken ownership of its new geothermal power station north-east of Taupo.
The $475 million Ngatamariki plant had been in a testing phase and reached its full capacity for the first time in June.
Mighty River Power chief executive Doug Heffernan says the 82-megawatt plant produces enough electricity to power about 80,000 homes.
He says geothermal energy now accounts for about 40% of the company's total generation.