Meridian Energy says the Christchurch earthquake and abnormally high spot power prices during March, hurt its earnings.
Wholesale electricity prices soared to nearly $20,000 per megawatt hour during a six-hour maintenance shutdown on the national transmission grid in March.
Fourteen parties, including Meridian, have lodged claims with the Electricity Authority about the spike and have asked for a correction
Meridian says that assuming the prices from that day will be final, earnings will fall to $33.62 per megawatt hour in the first three months of the year, from more than $50 per megawatt hour in the previous quarter.
The company says customer numbers rose from 263,000 to more than 267,000 during the period and competition remains intense.
Meridian says national storage levels are above average and while wholesale prices are expected to remain low in the short term, it expects to meet its targets.