Genesis boss Marc England has rejected claims New Zealand had enough power to handle the unprecedented demand last night, but that commercial decisions had caused widespread outages.
Energy and Resources Minister Megan Woods said today she was seeking assurances from the country's power companies that they were not trying to keep prices high by generating low amounts of electricity.
She said the power outages experienced by many New Zealanders last night were a result of "commercial decisions" made by the electricity companies.
"This wasn't a physical constraint of generation," she said.
"We did have the ability to generate the amount of electricity that we needed to keep the lights and the heaters on for New Zealanders last night but commercial decisions were made not to."
However, Genesis CEO Marc England told RNZ's Checkpoint this evening his company was being scapegoated by Woods, and denied it was a commercial decision to have less supply. He said it had been an operational decision.
"Genesis is just one of several generators. We actually lost a lot of money yesterday. More than $1 million," he said.
England said a build-up of weeds in a hydro lake and a lack of wind for turbines had hampered supply.
Transpower apologised this morning over the cuts on one of the coldest nights of the year.
'Not a tolerable situation' - Woods
Woods said she would seek assurances the market would continue to generate enough electricity.
"I don't think that is a tolerable situation. I think if we did have a situation where there was such a constraint of the generation of electricity in New Zealand and New Zealanders could not be sure of their ability to keep the lights on and the heater on then we have some serious questions," Woods said.
A spokesperson for Genesis said today that an unusual combination of both too much wind and too little wind meant it was not generating as much electricity as it had hoped.
At the Tokaanu hydro project, "gale-force winds earlier in the day pushed weed into the intake", resulting in less generation capacity.
This was followed by "a sudden decline in wind in the evening that affected central North Island wind generation - including Waipipi wind farm".
"As weather conditions improve we expect the issues [at] Tokaanu to be resolved and demand to fall to more normal levels." the spokesperson said.
Genesis said Huntly did not bring on additional capacity by turning on its third coal-fired Rankine unit, because each unit takes several hours to turn on.
Because the issues at Tokaanu and on the wind farms occurred suddenly, Genesis said it would not have had enough time to fire up the Rankine unit to meet additional demand.
Transpower, which manages the overall electricity network, also came under fire from Woods for failing to forecast the amount of load that needed to be shed from the network to keep it functioning.
This led to something of an overreaction.
"There was an overestimation by Transpower of how much needed to be shed.
"The number they were putting out to the distribution networks, to the lines companies, was that 2 per cent needed to come off. It seems like that was probably double the estimate of what needed to be shed," Woods said.
- with RNZ