Cuts to continue as power use soars

National grid operator Transpower has warned consumers that water heating cuts will continue as long as the very cold weather lasts.

As snow fell yet again in the South Island, and 1400 Canterbury homes went into their 11th day without power, electricity use in the upper South Island surged to a new record.

Transpower spokesman Chris Roberts said: "If the weather continues like this, then we'll see ongoing use of hotwater cuts, and all the generators will be going flat out."

The immense power of New Zealand's week of storms has also been felt on the other side of the Pacific Ocean.

CBS news reported that a surge of waves initiated off the coast of New Zealand had battered homes and beachfront businesses from Peru to Mexico.

Hugh Cobb, a forecaster at the United States' National Hurricane Centre in Miami, said the waves resulted from a particularly intense low pressure system several hundred kilometres off New Zealand that caused hurricane force winds and snowfalls at sea level.

"The storm system that generated these waves was fairly extraordinary," Mr Cobb said.

Transpower has been asking generators to ramp up supply. Lines companies are being told to "shed load", mostly by switching off hotwater heaters.

"We've been asking lines companies to control hot water for up to three hours a day," said Genesis Energy spokesman Richard Gordon.

There was plenty of supply, he said, but some areas of the country, such as the western Bay of Plenty, had "constraints" on how much power could be fed to households.

Graham Petrie, the network operations manager of Auckland's major electricity supplier Vector, said turning hot water off was a common international method of reducing the load.

"At about 5pm the load starts to ramp up because everyone gets home and starts turning on heaters and cooking. So ... we start to do load control by turning hot water heaters off."

He said hot water cylinders in any one area could go off intermittently during the day.

Lines company Powerco "shed customers" - 6000 of them - as demand threatened to overload transmission lines in the western Bay of Plenty near Te Puke during Monday's record demand.

Power was cut at 5.40pm, when national grid controller Transpower issued an emergency grid notice, and reconnected at around 8pm.

- additional reporting: NZPA