The failure was caused by damage to a power line supplying the Kurnell peninsula that occurred while state-owned utility Energy Australia was undertaking work.
Production of finished products such as petrol, diesel and jet fuel was affected.
Caltex chief executive David Reeves declined to put a figure on the loss on Wednesday, but it understood the cost is likely to be in the tens of millions of dollars.
An 18-minute power blackout at the same refinery in 1995 resulted in Caltex receiving a $7.25 million insurance payout.
Reeves would not comment on whether Caltex would seek damages from Energy Australia over the incident.
