Aucklanders' love of trees contributed to power cuts to a quarter of the region during Tuesday night's storm, an electricity industry commentator says.

Wellington-based Molly Melhuish said people's reluctance to remove or trim trees exacerbated the effect from the strong winds, which gusted more than 150kmh overnight.

VECTOR Vector crews work to restore power after a fallen tree blocked a road in West Auckland's Swanson.

"I love trees on streets, I don't want to be too hard on getting rid of them, people love their trees, they hate cutting them down, but they've paid the price this time," Melhuish said.

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Protecting properties' power supplies "depends on how strongly Vector insists on removing dangerous trees, that's what all the outages were about", she said.

About 120 power lines remained down, with more than 91,000 Auckland properties without power on Wednesday, and some could be without it for days, Vector network manager Minoru Frederiksens​ said.

Vector had 75 crews working to restore lines but that could take two to three days, he said.

Vector spokesman Iain Butler confirmed "by and large" trees were to blame for Auckland's outages.

SUPPLIED "I love trees on streets, I don't want to be too hard on getting rid of them, people love their trees, they hate cutting them down, but they've paid the price this time," Molly Melhuish said.

"A tree doesn't have to fall to cut power. Smashing into lines and then blowing back again can be enough, and not all fallen trees land on power lines," Butler said.

The company's hands are often tied wanting to trim trees that they need permission from property owners to prune, Frederiksens said.

Even if permission is granted, property owners don't want to pay trimming costs and Vector is reluctant to pick up the tab for what he said is the tree owner's responsibility.

ABIGAIL DOUGHERTY/STUFF Vector often wants to trim trees, but needs permission from property owners, its network manager Minoru Frederiksens said.

"More trees" weakened by Tuesday's cyclone force winds and heavy rains could come down and cause more outages if another low front deepens and strikes Auckland, he said.

EMA: AUCKLAND'S GRID AND BUSINESSES 'RESILIENT'

JOHN SELKIRK/STUFF Auckland has "one of the best power supplies" but "there's not a lot you can do" about storms hitting power lines, Employers and Manufacturers Association chief executive Kim Campbell said.

Employer and Manufacturers Association chief executive Kim Campbell's initial assessment on how Auckland's grid stood up in the "phenomenal storm" was positive.

Winds peaked at 213kmh at Manukau Heads.

Campbell said work started following Auckland CBD's crippling six-month-long outage in 1998 had made the city's power grid more robust.

By world standards, the city had "one of the best power supplies", but "there's not a lot you can do" about storms hitting power lines, he said.

All businesses should have contingency plans for power outages, he said.

Most businesses have business interruption insurance and larger firms have backup power generation.

"There's is no power grid in the world which is 100 per cent reliable. We have a storm that happens once every 50 years so we have an outage that lasts a few days.

"If this happened every week then you'd say 'we've got a problem'."

RESTORATION PRIORITIES

CHRIS MCKEEN/STUFF Lines company Vector said fallen trees were to blame for most of Auckland's power outages.

Vector said it first must restore larger 'feeder' power lines to get as many Auckland households reconnected.

Essential services like hospitals are also a priority as are large buildings and hot water circuits.

Molly Melhuish said Auckland's power outage was a good wake-up call for people to create and modernise household survival kits.

People's disaster kits should not only include fresh water, torches, food and food heating equipment suitable for 48 hours, they should also have 'power banks' able to recharge cellphones and other electronic devices.