Power has been restored to 90 per cent of the properties that were affected by a major power outage in the North Island this afternoon.

Transpower said a connection to the Huntly power station was lost at 12.30pm. As a result, up to 500 MW of power supply was shed in the North Island to protect the transmission system.

Transpower has now restored power to the system but it was up to the distribution companies to reconnect their customers, a spokeswoman said.

Acting Minister of Energy and Resources, Hekia Parata said her officials had been in contact with Transpower throughout the day.

''By 5pm tonight, 90 per cent of the supply had been restored.

''I will continue to receive updates throughout the restoration process,'' she said.

Widespread outages were reported throughout the Auckland and Wellington regions, however reserve generation being brought online meant power had been restored to most Auckland consumers.

Water heating would still be affected, however.

Genesis Energy confirmed about 30 per cent of the North Island had been affected by outages.

Vector earlier said electricity had been cut to thousands of Auckland customers from north of the Harbour Bridge to Wellsford, and Hillsborough in the west had also been affected.

However the company had been given the green light to restore power to its Auckland customers.

In the lower North Island Stuff readers across Wellington, Lower Hutt and as far north as Whitby said the power had been out for nearly an hour.

Saeran Maniparathy said they lived in Normandale and nothing would work.

"We were in the Lower Hutt CBD and there was no power there either. Queensgate mall had no power. We have friends in Whitby, no power there either."

Power went out at Queensgate Mall at 12.45pm. Police officers were stationed at mall entrances and retailers guarded their storefronts while confused shoppers milled around.

Kelly Sutton, who owns the The Florist Queensgate, said the outage was a major financial blow to herself and other retailers. "We are ten days out from Christmas, the mall was chocka (sic). It was right in the prime of the lunch rush."

Lights have now started to come on in parts of the mall but some areas remain cordoned off.

Residents also reported outages in Hawke's Bay, Taupo and Taranaki.

Around 20 per cent of Taupo and Rotorua were without power, said Unison spokesman Danny Gough said.

Gough said there were "pockets" of areas without power in and around Taupo.

"It is not widespread but has caused loss of power to 20 per cent of our customers in Taupo, Rotorua and Hawkes Bay,"he said.

Areas affected in Taupo included parts of the main business shopping area and the city's AC Baths had lost power.

Gough said "staged" resoration was underway to restore power to customers.

TRAFFIC DISRUPTED

Traffic lights in affected areas were not working, with large traffic delays reported in parts of Auckland due to the power outage.

The outage was also affecting traffic lights along State Highway 2 on the Hutt motorway in Wellington, NZTA reported.

Drivers were encouraged to use common sense, police central communications shift manager Andy Dow said.

"Give way to your right - Just treat it as an uncontrolled intersection," he said.

Drivers were having to queue for petrol with many stations in Petone and Lower Hutt without power.

The Shell station on Hutt Rd was one of just a handful open with queues of cars waiting 10 minutes to fill up.

There had been no reports of any incidents related to the power outages and power at the police communication centres was still on, which meant 111 calls would not be affected.

OUTAGE 'WIDESPREAD'

Transpower spokeswoman Adele Fitzpatrick said it was unclear what caused the fault, or how many customers were affected, although the outage was described as ''widespread" across the North Island.

''Some of the customers would have only been off for a very short time, we started restoring quite quickly, others will take a little longer.''

There was no indication of how long it would be before all customers had supplies restored.

About 94,000 customers across Powerco's network lost power at 12.30pm. All Powerco customers have now had their power restored, a spokeswoman said.

Vodafone spokesman Matt East said customers in areas without power may have lost their fixed-line broadband connection or phone line connection, if they used a cordless phone.

About 80 of the company's cell sites had switched to back-up power after losing their mains supply, but all were now back running on mains power, he said.

He was not aware of any customers unable to call 111 because of the outage.

Telecom spokesman Mark Watts also said he understood there had been no incidents where people had been unable to call 111.

"There will be some people affected but we're not aware of any widespread issues. The latest information I have is that power is being restored and the impact on our sites and services has been pretty minimal," Watts said.