Power back for all Aucklanders

Electricity has been restored to all homes and businesses in Auckland, two-and-a-half days after a power cut hit 85,000 properties, lines company Vector says.

However, a spokesperson said not everyone's power supply would stay on for long, as some pockets of Orakei, St Heliers and Remuera could drop off again during tonight's evening peak.

Hot water would also continue to be affected until this evening, as Vector would control hot water on part of the network in a bid to lower the pressure on supply as two more cables are brought into service tonight.

Energy Minister Simon Bridges said an inquiry into the cuts, caused by a fire at Transpower's Penrose substation on Sunday morning, would look into the overall impact on the city's economy but not at individual compensation cases.

He had asked the Electricity Authority to carry out a full inquiry into the power cuts.

Prime Minister John Key yesterday said there needed to be a review of the two-day power cut, which plunged tens of thousands of homes into darkness.

Mr Bridges said either the Electricity Authority or a ministry could hold that inquiry.

"Firstly we need to determine what and who, if you like, was at fault, I think then, very much, it is a matter for consumers and businesses to take up with their retailers."

Mr Bridges said it looked like lines company Vector had acted appropriately in the immediate aftermath of the power cut but the inquiry would consider that more closely.

Business takes a hit

Businesses at the country's biggest retail mall, Sylvia Park, said they been hit hard by the power cut.

The mall has reopened but businesses say they lost up to $10,000 each in trade, having missed out on what was expected to be a busy Sunday during the school holidays.

Food outlets report high food wastage, with one ice-cream store throwing away 90 lots of 5 litre tubs.

As well, production at Tiptop's ice-cream factory in Auckland is still in limbo the blackout.

Fonterra managing director Tim Deane said they did however manage to rescue all 4500 tonnes of ice-cream thanks to the installation of backup generators.

"We've lost none of that product. All of that product is safe," he said.

"We obviously lost about a day's production, so we were in the middle of producing ice-cream when the power outage occurred, so we've lost about a day's worth of manufacturing ingredients."

The company was yet to tally up how much the outage had cost it.

Fletcher Building general manager Philip King said the company lost power to 26 of its sites, including manufacturing plants, distribution centres, retail stores and its head office in Penrose and the blackout had cost it millions of dollars.

Auckland Chamber of Commerce chief executive Michael Barnett said many companies would not have business interruption insurance and would look to Vector to help to recover costs.

He also said Auckland would also have suffered damage to its reputation because of the fault.

Vector spokesperson Sandy Hodge said the main St Johns feeder was restored overnight.

Auckland University's energy expert, Dr Nirmal Nair, believes new infrastructure may be needed after the substation fire.

"The first stage of this investigation should decide on the cause of the fire, and really looking at how the cable got such massive damage."

He said the investigation should then look at whether there are any alternative backfeeds available.

Dr Nair, however, said he did not believe there had been under-investment in the network as a whole.

Council for Infrastructure Development chief executive Stephen Selwood said Auckland's power cut highlighted an inevitable trade-off between security of supply and its cost to consumers.

A review of the network would have to consider whether there needed to be more resilience in the system - although he said there had been a huge amount of investment in the past few years.

Residents' association says it did not oppose substation

The Ellerslie Residents' Association said community opposition to a second substation in Ellerslie was not the reason for Auckland's power cut - as had been suggested by Mr Selwood yesterday.

But residents' association chair Bryan Johnson said the community was only opposed to the original site, which was close to a childcare centre and a busy street.

"After discussions with Vector we found out the need for that substation was related to the developments on the race course, so the logical conclusion was then 'why isn't the substation being built on racecourse land?"

He said there was now an in-principle agreement between Vector and the racecourse to do so, with construction starting in 2018.