The national grid operator Transpower has apologised for its shortcomings that led to widespread power blackouts in August.
Last month, the Electricity Authority said Transpower's systems for allocating demand and its communication were unsatisfactory and confused local lines companies, leading to the blackouts affecting 34,000 people on one of the coldest nights of the year.
Transpower has released its own independent report into the incident this afternoon.
It said the root cause was a shortage of generation due to the combined effect of planned generation outages, the lack of market pricing signals to incentivise the offer of available slow-start thermal generation, and the unexpected loss of hydro and wind generation.
The blackouts occurred on the evening where New Zealand saw its highest electricity demand ever, Transpower said.
It admitted operational procedures, communication and error in demand allocation exacerbated the issue, resulting in additional households losing electricity for a short period of time that evening.
"New Zealand has not experienced an event like this since 1992 and it is our intention to avoid a repeat," chief executive Alison Andrew said.
"We have contributed to the Electricity Authority's phase one review and have accepted all recommendations made by the Authority. Work is already underway on implementation.
"We are also contributing to the review being led by the Ministry of Business, Innovation and Employment."
The report also identified that Transpower's lack of visibility over the use of controllable load by distribution networks was a barrier to the effective management of such an event.
"These issues are wider than Transpower in its role as the system operator and avoiding a repeat of August 9 will require the commitment of the entire industry," Andrew said.
"Transpower as system operator plays a key role in the co-ordination of the electricity market and it is a responsibility we take very seriously. Looking ahead success will also require active industry involvement in addressing the issues highlighted."