Government investigation finds August power cuts were unnecessary

Energy Minister Megan Woods has asked for changes after an investigation found that 34,350 homes needlessly had their power cut off without warning in August.

National grid operator Transpower ordered lines companies to reduce their power usage on the evening of August 9, after a cold snap that was forecast to leave supplies tight coincided with an unplanned outage of Genesis’ Tokaanu hydro power station on the Tongariro River.

The goal of ordering the cuts was to protect the grid and prevent wider disruption to electricity supply.

A report headed by former minister Pete Hodgson and assisted by technical advisor Erik Westergaard concluded that the power cuts, which lasted up to two hours, “simply need not have happened” as there was enough power that evening, Woods said.

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It had previously emerged that most of the homes would not have had their power cut, had Transpower not made an error in calculating the cuts that it thought some lines companies needed to make to achieve the reduction it was targeting.

But Hodgson’s report found lines companies had made all the savings necessary by using ripple control to remotely turn off hot-water heaters, and that the power cuts were therefore “entirely avoidable”.

An issue was that Transpower did not have full visibility of the power savings that had been made, it found.

“Ensuring that the system operator has accurate real-time awareness of the size of each electricity distribution businesses’ discretionary load is a central recommendation,” the report said.

But it also said the ripple control system used to remotely manage hot-water heaters was “at risk of decay” and there was an opportunity for power firms to manage demand from electric-vehicle chargers and smart appliances to help cope with future situations when power supplies were tight.

“There is some urgency in progressing these things,” it said.

Woods said she had written to the chairs of Transpower and the Electricity Authority requesting they consider the report’s recommendations and update her each quarter on their progress.

“I do not want households to be put in this situation again. By implementing the report’s 18 recommendations I believe we will be better placed in future,” she said.

It was clear the electricity industry would need to be better able to control demand as it moved towards using more renewable energy, Woods said.

“In future, better use of hot water control, known as ripple control, and other technologies are likely to be key to this,” she said.