Key Points:

The North Island is facing the prospect of blackouts today if its aging electricity system fails to cope with a major power station shutting down.

Contact Energy's 380 megawatt (MW) combined-cycle power station in Taranaki was due to be shutdown for 60 days this morning.

A breakdown at the plant last Friday, combined with a lack of wind for wind-generation, high water temperatures in the Waikato River and an inter-island link constrained to only 400MW pushed up power prices and caused concern about power cuts.

Auckland electricity consultant Bryan Leyland said yesterday the shutdown raised real concerns about how the system would cope without the Contact plant.

"If the weather and conditions are the same as today, it is difficult to see how we will get through (Friday) without load shedding and the possibility of blackouts," he told The Press.

"It won't affect the South Island. There's only one thing they can do - if it gets too bad, they might run the link up to 700MW, which will give them another 300MW, which is more or less equivalent to what they have lost.

"But in that case we're at risk of losing the DC link, which would for sure cause blackouts."

Contact spokesman Jonathan Hill told the paper the maintenance at the Taranaki power station could not be delayed, having been scheduled for more than a year and involving 50 engineers from Sweden.

"It's critical we get this plant up and running for winter."