The cause of a five-hour power cut which affected thousands of Far North households and businesses was still a mystery hours after the outage ended yesterday afternoon.

The power went out at 9.07am across the top half of the Far North, from North Hokianga to the northern side of Whangaroa Harbour. The affected area included Kaitaia, Ahipara, Mangamuka and the Karikari and Aupouri peninsulas.

At the peak about 10,000 homes and businesses were affected. Communication was disrupted when some cellphone sites stopped working.

Lines company Top Energy sent a helicopter and ground crews to inspect the 110kV line between the Kaikohe substation and Kaitaia but was unable to locate the fault, spokeswoman Philippa White said.

Advertisement

Even after power was restored in Kaitaia just before 2.30pm the cause remained unclear. A second, unrelated fault meant power was still out at Ahipara and Herekino at 5pm yesterday.

Parts of Doubtless Bay - including Mangonui, Taipa, Oruru and Tokerau - missed the worst of the power cut thanks to two 2MW back-up diesel generators at Taipa, installed by Top Energy in 2012 when the area had the worst record of outages in the Far North.

In Kaitaia the latest power cut was met with a mix of frustration and resignation.

Many shops, service stations and eateries closed, some limped on without Eftpos or electronic tills, and others had installed generators after previous blackouts.

Kaitaia's Pak 'n Save, which includes a petrol station, has its own power supply, as does the hospital and the Juken NZ-owned timber and triboard mills, the town's biggest employer.

Antony Pedersen, of Carters building supplies, said his store stayed open by switching to manual processing of sales.

"It's painful but it does the job," he said.

Craig Rogers, of Rogers and Rogers plumbers, said after the December power cut he had hard-wired a generator into the office to at least keep computers and phones running.

"It happens a couple of times a year. It's a bit frustrating, we can't afford not to be operating."

The generator would quickly pay for itself by preventing staff downtime.

For some businesses, however, it was simply a case of waiting it out.

Tyler Bamber, owner of The Bushman's Hut restaurant, said he had been "sitting in the dark hoping we'd have power for dinner".

His losses were not huge because he did most of his business in the evenings but it was frustrating nonetheless.

"If this happened in Auckland it would be all over the news. It seems we're forgotten about, that services drop off the further you get from Auckland or Wellington."

The geothermal power station at Ngawha could not help because the fault was further north. Top Energy is building a second transmission line east of the current Kaikohe-Kaitaia link. Once complete it is expected to reduce the number of outages in Kaitaia.

On December 8 last year the entire Far North lost power for 12 hours when members of a hunting party shot out insulators on power pylons in a remote area near Matawaia. The power went out about 3am and was restored after 2.30pm.