The Marsden Point oil refinery says it lost hundreds of thousands of dollars in Friday's power outage.
Some 280,000 customers in Northland and parts of Auckland had their power supply cut when a forklift carrying a container hit a high voltage line in Otahuhu at 8am while the alternative line was out for maintenance.
Power was restored to most Auckland customers by 10.30am and Northland by 1pm.
As a priority industry, the refinery had power restored by 9am. It operates 24 hours a day and depends on a continuous power supply.
The New Zealand Refining Company says a second secure power source would have prevented the outage.
While the refinery lost revenue, chief executive Ken Rivers says the wider issue is that fuel suppplies to Auckland could have been totally disrupted.
The company said on Friday it would take some time to restart all the processes and find out how much product was lost.
