A half-billion dollar upgrade to help provide a secure power supply to the upper North Island is now on line.
Transpower said the latest addition to the national grid - the North Auckland and Northland project - went into full operation at 10am on Wednesday.
Power will flow across Auckland through the new cable running from Pakuranga to Albany, supported by two new substations at Wairau Road and Hobson Street, along with other upgrades.
Transpower chief executive Alison Andrew said the $473 million project addressed the region's reliance on a single transmission live.
She said it provided an alternative route and a more reliable power supply for the country's largest commercial centre.